University of Dundee 6-10 April 2014 - RSC ESR Spectroscopy...

The 47th Annual International Meeting of the ESR Spectroscopy Group of the

Royal Society of Chemistry

CONFERENCE PROGRAMME

University of Dundee 6-10 April 2014

Contents

Conference Programme 1

The Bruker Lecture 6

JEOL Student Prize Lectures 7

Information for delegates 8

Conference accommodation and travelling between venues 8

Speaker information 12

Poster presenter information 12

Accommodation 12

Internet access 12

Car parking 12

Taxis 12

Checking out and left luggage 12

Travelling to Dundee

By car, air, rail, Coach 13

Travelling to your Hotel 14

Local highlights within walking distance of the conference 14

Free Afternoon: Tuesday 8th April 15

Useful Contact Information 17

Poster presenter information 18

Committee of the ESR spectroscopy Group of the RSC 20

Conference sponsors 21

Conference Delegate List 22

Abstracts for Talks K1-‐‑O33

Abstracts for Posters P1-‐‑P32

The 47th International Meeting of the ESR Spectroscopy Group, Dundee 2014

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The 47th Annual International Meeting of the ESR Spectroscopy Group

of the Royal Society of Chemistry University of Dundee

6-10 April 2014

Conference Programme

All sessions to be held at the Invercarse Hotel 371 Perth Rd, Dundee, Dundee City DD2 1PG

01382 669231

Sunday 6th April 16.00 – 18.00 Registration 18.30 – 20.00 Dinner Invercarse Ballroom 20.00 – 22.30 RSC Reception Monday 7th April 08.55 – 09.00

David Keeble & David Norman

Welcome and Conference Opening

Sessions Session 1 Chair: Dimitri Svistunenko 09.00 – 09.40 K1 Tom Owen-Hughes Keynote lecture: PELDOR measurements as a

means to address structural puzzles in chromatin 09.40 – 10.00 O1 Eric McInnes Antisymmetric exchange effects in transition ion

clusters 10.00 – 10.20 O2 John Walton EPR Inquisition of Radicals Released from Oxime

Derivatives 10.20 – 11.00 Coffee & Registration Session 2 Chair: David Collison 11.00 – 11.30 I1 Gunnar Jeschke Invited lecture: New Developments in Ultra-

Wideband EPR 11.30 – 11.50 O3 Gareth Eaton Rapid-Scan EPR and EPR imaging 11.50 – 12.10 O4 Mohamed Morsy Drug Analysis using Electron Paramagnetic

Resonance (EPR) Spectroscopy

12.10 – 12.30 O5 Sandra Eaton Frequency Dependence of Electron Spin Lattice Relaxation for Rapidly Tumbling Radicals

12.40 – 14.00 Lunch

The 47th International Meeting of the ESR Spectroscopy Group, Dundee 2014 2

Session 3 Chair: Eric McInnes 14.00 – 14.20 O6J Maya Abou Fadel JEOL Talk: Chemometrics tools for the separation of

chemical contributions in EPR spectroscopy 14.20 – 14.40 O7J Luca Garbuio JEOL Talk: Gd(III) – nitroxide DEER on proteins:

chemo-selective labelling, technique optimization and combination with paramagnetic NMR

14.40 – 15.00 O8J Thomas Keevers JEOL Talk: Spectroscopic Investigation of Spin-Dependent Optoelectronic Path-ways in Organic Devices

15.00 – 15.20 O9J Daniel Klose JEOL Talk: Tracing the transient conformational signal in bacterial phototaxis using SDSL-EPR spectroscopy

15.20 – 16.00 Tea & Coffee Session 4 Chair: Ilya Kuprov 16.00 – 16.20 O10J Eline Koers JEOL Talk: NMR-based Structural Biology enhanced

by Dynamic Nuclear Polarization at high magnetic field

16.20 – 16.40 O11J Johannes McKay JEOL Talk: Orientation selective PELDOR measurements of the RX spin label

16.40 – 17.00 O12J Claudia Tait JEOL Talk: EPR study on triplet state delocalisation in conjugated porphyrin systems

17.00 – 17.20 O13J Mika Tamski JEOL Talk: Electrochemical Electron Paramagnetic Resonance utilizing microelectrodes and loop gap resonators

18.00 – 19.30 Dinner Invercarse Ballroom 19.30 – 22.00 JEOL Reception &

POSTER SESSION


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Tuesday 8th April Session 5 Chair: David Keeble 09.00 – 09.40 K2 Christoph Boehme Keynote lecture: Pulsed Electrically Detected

Magnetic Resonance Spectroscopy of Organic Semiconductors

09.40 – 10.00 O14 Aharon Blank High Resolution Microimaging with Pulsed Electrically-Detected Magnetic Resonance

10.00 – 10.20 O15 Shigeaki Nakazawa A ground-state triplet iminonitroxide-nitroxide diradical in magnetically diluted single crystal as studied by CW-ESR/pulsed ESR spectroscopy

10.20 – 11.00 Tea & Coffee Posters Session 6 Chair: Mark Newton 11.00 – 11.30 I2 Stephen Lyon Invited lecture: Low power high sensitivity pulsed

ESR for quantum information 11.30 – 11.50 O16 Alice Bowen Towards a Molecular-Magnet based Quantum

Computer: Double Electron-Electron Resonance Analysis of Two Qubit Metal-Ring Dimers

11.50 – 12.10 O17 Takeji Takui NMR-paradigm pulse ESR spectroscopy: Coherent multi-frequency spin manipulation technology for spin-based quantum computers and quantum information processing

12.10 – 12.30 O18 Christopher Kay Potential for spin-based information processing in a thin-film molecular semiconductor

12.40 – 14.00 Lunch Posters

FREE AFTERNOON 18.00 – 19.30 Dinner Invercarse Ballroom Session 7 Chair: Graham Smith 19.30 – 19.40 Mark Newton Introduction 19.40 – 21.00 Jörg Wrachtrup Bruker lecture: Shedding light on single spins 21.00 – 23.00 BRUKER Reception


Wednesday 9th April Session 8 Chair: David Norman 09.00 – 09.40 K3 David Cafiso Keynote lecture: Membrane fusion. A tale of protein

conformational exchange, self-association and structural heterogeneity

09.40 – 10.00 O19 Bela Bode Pulse EPR distance measurements on homo-oligomers – from dimer formation to multi-spin artefacts

10.00 – 10.20 O20 Katharina Pirker Structural insight into (human skeletal muscle) alpha-actinin protein using SDSL in combination with cw and pulsed EPR

10.20 – 11.00 Tea & Coffee Session 9 Chair: Bela Bode 11.00 – 11.30 I3 Gail Fanucci Invited lecture: Spin-Labeling Studies of Protein

Conformational Flexibility 11.30 – 11.50 O21 Richard Ward Mechanosensitive channel of small conductance in

lipid bilayers studied by PELDOR at X and W band 11.50 – 12.10 O22 Johann Klare Influence of mutations on conformational changes

during GTP hydrolysis in an ortholog of the human LRRK2 Parkinson kinase analysed by DEER

12.10 – 12.30 O23 Katerin Ackerman PELDOR spectroscopy identifies new structural features of strepto-coccal M3 protein

12.40 – 14.00 Lunch Session 10 Chair: Fraser MacMillan 14.00 – 14.40 K4 David Britt Keynote lecture: Assembling the H-Cluster of

[FeFe] Hydrogenase 14.40 – 15.00 O24 Edgar Groenen Continuous-wave EPR at 275 GHz: the case of

pseudoazurin 15.00 – 15.20 O25 Christian Teutloff Monitoring large domain movements in CoFeSP of

Carboxydothermus hydrogenoformans during activation

15.20 – 16.00 Tea & Coffee Session 11 Chair: Christopher Kay 16.00 – 16.30 I4 Sabine Van Doorslaer Invited lecture: Neuroglobins – a playground for

EPR spectroscopy 16.30 – 16.50 O26 Maxie Roessler The O2-tolerant hydrogenase from E. coli and some

insights into the unique [4Fe-3S] cluster 16.50 – 17.10 O27 Alistair Fielding Advanced electron paramagnetic resonance on the

catalytic iron sulphur cluster bound to the CCG domain of heterodisulfide reductase and succinate: quinone reductase

17.10 – 17.30 O28 Dimitri Svistunenko Haptoglobin binding to haemoglobin changes the microenvironment of αTyr42, effecting in a lower reactivity of its radical state generated by H2O2 : a stopped-flow EPR study

17.30 – 18.00 AGM RSC ESR Spectroscopy Group 18.15 Departure Coaches to St Andrews 19.30 – 23.30 Conference Banquet,

Ceilidh, and Prizes Lower College Hall, University of St Andrews


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23.30 Departure Coaches to Dundee Thursday 10th April Session 12 Chair: Alistair Fielding 09.20 – 09.40 O29 Fraser MacMillan PsaBCA and manganese acquisition: Elucidating

the molecular basis of metal ion selectivity and binding by Gram positive bacteria

09.40 – 10.00 O30 Vasily Oganesyan Probing nematic and discotic liquid crystals by a combination of EPR spectroscopy and theoretical modelling

10.00 – 10.20 O31 Ilya Kuprov Pseudocontact shift from distributed paramagnetic centres

10.20 – 11.00 Tea & Coffee Session 13 Chair: Gavin Morley 11.00 – 11.30 I5 Mark Newton Invited lecture: Hydrogen in diamond: Defects and

Diffusion 11.30 – 11.50 O32 Jan Behrends Charge Separation in Organic Solar Cells probed

by Transient EPR 11.50 – 12.10 O33 Chris Wedge Spin-locking in low-frequency RYDMR 12.10 – 12.30 Graham Smith Closing Remarks 12.30 – 14.00 Lunch

CONFERENCE END: DEPARTURE


The 47th Annual International Meeting of the ESR Spectroscopy Group of the Royal Society of Chemistry

The Bruker Lecture

From 5:30pm The Invercarse Hotel

Professor Jörg Wrachtrup Professor of Physics and Institute Director, 3rd Physical

Institute, University of Stuttgart

“Shedding light on single spins”

Followed by the BRUKER Reception

9 – 11 pm


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JEOL Student Prize Lectures Sessions 3-4

2-6pm, Monday 7 April 2014 The JEOL competition is open to postgraduate students in their second or third year of research and postdoctoral fellows in their first year. The fifteen-minute talks are judged by the ESR Spectroscopy Group Committee and the winner chosen on the basis of scientific content and delivery. The engraved medal and prize, generously sponsored by JEOL, will be presented to the winner at the conference banquet, to be held on Wed 9 April 2014 at St. Andrew’s University, Lower College Hall. Maya Abou Fadel: Chemometrics tools for the separation of chemical contributions in EPR spectroscopy Luca Garbuio: Gd(III) – nitroxide DEER on proteins: chemo-selective labelling, technique optimization and combination with paramagnetic NMR Thomas Keevers: Spectroscopic Investigation of Spin-Dependent Optoelectronic Path-ways in Organic Devices Daniel Klose: Tracing the transient conformational signal in bacterial phototaxis using SDSL-EPR spectroscopy Eline Koers: NMR-based Structural Biology enhanced by Dynamic Nuclear Polarization at high magnetic field Johannes McKay: Orientation selective PELDOR measurements of the RX spin label Claudia Tait: EPR study on triplet state delocalisation in conjugated porphyrin systems Mika Tamski: Electrochemical Electron Paramagnetic Resonance utilizing microelectrodes and loop gap resonators

Followed by the JEOL Reception & Poster Session 7:30-10pm


Conference accommodation and travelling between venues

The Invercarse Hotel If you have been booked into the Invercarse Hotel (371 Perth Road, Dundee, DD2 1PG) this hotel is about 3-4 km out in the western suburbs and where the conference is to be held. http://www.bestwestern.co.uk/hotels/invercarse-hotel-dundee-83440/hotel-info/default.aspx If you arrive be train you can get a taxi to the Hotel for approximately £7. There is a good bus service also, but for this you need to walk up on to the High Street. There is a lot of construction work in progress fairly close to the station, but the town centre is signposted. You’ll cross a city dual carriage-way, you will see the Malmaison Hotel on your right, and Union Street ahead of you. The High Street is at the top of Union Street, turn left and you will see the bus stops. The National Express No. 5 bus is very regular through the day. It will take you to the ‘Glamis Road’ stop just opposite the Invercase Hotel on the Perth Road; this costs £1.90 and takes approximately 15 mins. If you think you will be making more than one journey you can buy a day pass for £3.50 (or a 7-day pass for £12.50). There are also StageCoach buses running along the same route, the No. 16, No. 96 or No. 42.

Red line indicates the route to walk from the rail station to the bus stops on the high street


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Map showing the location of the invercarse hotel (conference venue) and the rail station. The Holiday Inn Express If you have been booked into the Holiday Inn Express (41 Dock Street, Dundee, DD1 3DR) this hotel is in the centre of the city. The conference will be taking place at the Invercarse Hotel (371 Perth Road, Dundee, DD2 1PG) which is about 3-4 km out in the western suburbs. The Invercarse has excellent facilities, but has only limited number of rooms. The Holiday Inn Express is only a short walk (5 mins) from Dundee rail station, or from the bus station. There are quite extensive works in progress on the waterfront in Dundee, including near the rail station; the walkways should be sign posted but don’t be afraid to ask directions (Dundee people are very friendly). Follow the signs for the centre, you’ll cross a city dual carriage-way, you will see the Malmaison Hotel on your right, walk round on the south side and continue east on Dock St, you will come to Commercial St and the Hotel is on the opposite corner. If you really don’t want the walk then there is a taxi rank outside the station exit and the journey should only cost a few pounds (minimum fare). The following link gives access to more information. http://www.hiexpress.com/hotels/gb/en/dundee/dndee/hoteldetail/directions The registration desk at the Holiday Inn Express will be open from 4pm until we head over to the Invercarse for dinner. We will be running transport from the Holiday Inn Express to the Invercarse and back Sunday to Thursday. On Sunday we shall be providing a minibus service to the Invercarse between 16:00 and 18:00 and there will be a coach back after the drinks reception. If you need to travel outside the times the coaches are running then there is an excellent bus service. The National Express No. 5 bus can be caught from just outside the Invercarse on the Perth Road – the stop is called ‘Glamis Road’ and you will get off in town at the ‘Commercial St’ stop opposite Waterstones Book Shop; this costs £1.90 and takes approximately 15 mins. If you think you will be making more than one journey you can buy


a day pass for £3.50 (or a 7-day pass for £12.50). There are also StageCoach buses running along the same route, the No. 16, No. 96 or No. 42 will all get you from the Invercase back into town. Should you want to take a taxi it will cost approximately £7.

Map showing the location of the Invercarse Hotel (conference venue) and the rail station.


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Coach connections during the conference Sunday 6 April - Thursday 10 April Sunday 6 April 2014 22:00 pick-up Invercarse Hotel to Holiday Inn Express * Monday 7 April 2014 08:15 pick-up Holiday Inn Express to Invercarse Hotel 22:30 pick-up Invercarse Hotel to Holiday Inn Express Tuesday 8 April 2014 08:15 pick-up Holiday Inn Express to Invercarse Hotel 23:00 pick-up Invercarse Hotel to Holiday Inn Express Wednesday 9 April 2014 08:15 pick-up Holiday Inn Express to Invercarse Hotel 17:40 pick-up Invercarse Hotel to Holiday Inn Express Wednesday 9 April 2014 (evening) Dinner to be held at Lower Hall, St Andrews Departure, Invercarse 18:15, call in at Holiday Inn Express, then off to St Andrews to arrive for approximately 19:00. Return, pick-up at Lower Hall at 23:45 and a drop-off at the Holiday Inn Express then the Invercarse. Thursday 10 April 2014 08:50 pick-up Holiday Inn Express to Invercarse Hotel 14:00 pick-up Invercarse Hotel to Railway Station

*A mini bus (seats 14) will be available during the conference. The mini bus will specifically be available to transport attendees from the Holiday Inn to the Invercarse on Sunday afternoon. Exact times of pickup will be arranged on the day. Arrangements will be coordinated via the conference registration desk at the Holiday Inn, which will be occupied between 4pm and 6pm on Sunday.


Speaker information A Windows PC with PowerPoint and a projector will be provided. It will also be possible to attach a speaker's laptop to the projector. A laser pointer will be provided. If you require any other equipment, please inform the conference organisers. Please upload your presentation and/or test your laptop the day before your talk if at all possible. The duration of lectures is 60, 30, 20 and 15 min for Bruker, Keynote, Invited, and all other lectures respectively. Poster presenter information Posters will be displayed in rooms on the first floor of the hotel. Poster boards are A0 portrait format. They can be set up on Monday morning from 08.00, and will have to be taken down on Thursday before or shortly after lunch. Velcro stickers to attach the posters to the boards will be provided. Poster numbers will be displayed on the boards. There will be two poster sessions at the conference, for even and odd posters. However, the posters will be on display throughout the conference, and coffee breaks/receptions will be held near the posters. Accommodation Hotel accommodation will be either at the Invercarse Hotel or at the Holiday Inn Express in Dundee City Centre. For those not at the Invercarse Hotel, transport will be provided to supplement public transport. The address of the Invercase Hotel is 371 Perth Road, Dundee, Angus, DD2 1PG. Internet access There is free WiFi internet access at the Invercarse Hotel. Delegates wishing to connect to the internet must bring their own laptops and cables; there is one Internet connected PC available to guests, in the hotel lobby. Connection to WIFI requires the code ‘invercarse636’. Car parking The Hotels have free on site car parking for conference delegates. Taxis Taxis can be ordered from the hotel reception and numbers will also be supplied in the conference pack. Checking out and left luggage The delegates will need to check out of their rooms by 11 a.m. on the day of departure (before the end of the morning coffee break). It will be possible to store the luggage in a room adjacent to the conference reception on Thursday until the end of the conference.


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Travelling to Dundee By Car Dundee is linked to the rest of the UK by continuous motorway and dual carriageway - all the way from Devon and Cornwall. Dundee is best approached from the south via the A90 for traffic coming from Edinburgh (M90) and Glasgow (A9) and beyond. From the outskirts of Dundee the route into the University and the Medical School is well signposted and relatively easy to follow. Ninewells Hospital and Medical School is a prominent landmark on the approach to Dundee via the A90. There is also a scenic route from Edinburgh along the Fife coastline and into Dundee via the Tay Road Bridge. By Air Dundee airport is only five minutes drive from the University and has 4 flights a day to and from London City Airport. London City flights connect with many other destinations in the UK and Europe. Further information on flights to and from Dundee airport is available from CityJet or Dundee Airport Information Desk on +44 (0)1382 643242. International airports at Edinburgh, Aberdeen and Glasgow can be reached in 1 to 2 hours. By Rail Dundee is on the main East Coast route with direct services to Newcastle, York and London, and to Carlisle, Preston, Coventry, Birmingham, Oxford, Bristol, Reading, Southampton, Bournemouth and Plymouth. There are overnight sleeper services to and from London, the south coast and the west country. Rail journeys to the other major cities in Scotland (Aberdeen, Edinburgh, Glasgow) take approximately 1.5 hrs, and the regular service to and from London King's Cross takes less than six hours. The railway station is only a 10-minute walk from the University campus. Train times can be found from National Rail or by phoning the National Rail Enquiries Centre on 03450-484950. By Coach Day and night coach services (operated by National Express, Stagecoach, and Citylink) are available to major cities throughout the UK including London. Air www.cityjet.com/destinations/dundee/ Rail www.nationalrail.co.uk Coach www.nationalexpress.com/home.aspx Bus www.stagecoachbus.com/ Bus //www.citylink.co.uk/index.php

! ! !!

! The 47th International Meeting of the ESR Spectroscopy Group, Dundee 2014!!"+!

Travelling to your Hotel The Invercarse Hotel is a 5-minute drive from Dundee City Centre, Dundee Railway Station and from Dundee City Airport. The Holiday Inn Express is in the centre of town and a 5-minute walk from Dundee Train Station. Local highlights within walking distance of the conference venues: Information about what’s going on in Dundee: www.dundee.com Dundee Contemporary Arts: Film, Food, Bar Art and Cinema www.dca.org.uk Dundee Rep: Theatre and Restaurant www.dundeerep.co.uk The Overgate Centre: Shopping and Restaurants www.overgate.co.uk Discovery Point: History and Tour of the RRS Discovery www.rrsdiscovery.com The Dundee Botanic Garden www.dundee.ac.uk/botanic

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Free Afternoon: Tuesday 8th April

The period from the end of lunch at approximately 14:00 to dinner at 18:00 will be free on Tuesday. However, the lunch that day between 12:40-14:00 will be a light sandwich buffet so it may be possible to start the afternoon a little earlier. We make several suggestions below:

Dundee:

Dundee is a city with medieval origins, but dominated by the legacy of a Victorian to Edwardian era expansion based on, somewhat surprisingly, Jute from Bengal. It was also a major whaling port. The city is also the home of major newspaper publishing company, DC Thomson & Co Ltd, responsible for classic UK comics such as the The Beano and The Dandy – meet Desperate Dan and Mini the Minx outside the Caird Hall, City Square, complex. The surrounding countryside is ideal for growing soft fruits, for example the Carse of Gowrie stretching from Dundee west to Perth, originally this was mainly used for jam, these days it is mostly sold fresh. Dundee was famous for Jute, Jam, and Journalism. At the University, the Computing Department have recently moved out of the ‘Jam Factory’ and the EPR lab is located in what was originally a ‘Jute Shed’ (nice thick stone walls help to keep the temperature fairly constant). The large houses you will see long the Perth Road near the hotel are ‘Jute Mansions’ built by the owners of the business in the city. Unfortunately, the American Civil War provided an early spur to the industry; it was the first war to make fairly extensive use of jute sandbags.

The Invercarse Hotel overlooks the University Botanic Gardens and the Tay estuary. We have arranged for a guided walk by Dr Neil Patterson to be available at 2PM, places are limited so please sign up for this event. This will take approximately 1h.

You could then catch a bus from just outside the Invercarse into the city. The places we would recommend a number of activities within the city. The RRS Discovery, Captain Scott’s Antarctic expedition ship and museum is well worth a visit. Discovery was built in Dundee based on the technologies employed for whaling ships. The Verdant Works, an old Jute Mill, is also a good city museum. It is possible to buy a joint ticket covering both Discovery and the Verdant Works. The MacManus Art Gallery and Museum is an attractive building, recently renovated and features the earliest painting of a football match and Rossetti’s 'Dante's Dream on the Day of the Death of Beatrice'.

http://www.dundee.ac.uk/botanic/

http://www.rrsdiscovery.com/index.php?pageID=129

http://www.rrsdiscovery.com/index.php?pageID=130

http://www.mcmanus.co.uk/


St Andrews:

St Andrews is a small, but quite interesting, town. There is an excellent bus service from the Dundee Bus Station, the journey takes approximately 25 mins; there is a very regular bus service from the Glamis Road bus stop just outside the Hotel to the Bus Station. We may also be able to run a minibus.

Graham Smith and his team will also be hosting a laboratory visit to HiPER, the 1kW pulsed 94 GHz spectrometer, between 2-4PM. We will give more detailed instructions at the conference.

http://www.visitstandrews.com/

http://www.st-andrews.ac.uk/~mmwave/epr/hiper/

Nature Reserve Walk:

Weather permitting we also intend offering a walk through the Tentsmuir National Nature Reserve and Forest. The walk will start at Lundin Bridge and end at the Kinshaldy car park, a distance of approximately 7-8 km. The walk will be along forest paths and across sand dunes and beaches and requires sturdy walking shoes. A minibus will drop the group off, then pick them up.

http://www.tentsmuir.org/

Glamis Castle:

Glamis castle is a quite spectacular Scottish castle, childhood home of the late queen Mother. It is about 20 km north of Dundee. We can organise transport, probably a minibus, the cost of castle entrance is £10.90 and there may be an additional transport cost. There is a very pleasant walk through the grounds, with a fairly high chance of seeing red squirrels.

http://www.glamis-castle.co.uk/


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Useful Contact Information: Dr. David Norman Nucleic Acid Structure Research Group College of Life Sciences, University of Dundee, Dundee DD1 5EH Tel: +44(0)7808572788 Email: [email protected] Dr. David Keeble Division of Physics College of Arts, Science and Engineering Harris Building, Nethergate, University of Dundee, Dundee DD1 4HN Senior Lecturer & Head of Division Tel: +44 (0)1382 384561 Email: [email protected] Michelle Mulligan Divisional Secretary Biological Chemistry and Drug Discovery College of Life Sciences, University of Dundee, Dundee DD1 5EH Telephone: +44 (0)1382 385873 Email: [email protected] The Invercarse Hotel Martina Whiting 371 Perth Rd, Dundee Dundee City DD2 1PG Tel: +44 (0)1382 669231 Fax: (01382) 644112 Email: [email protected] www.bw-invercarsehotel.co.uk Holiday Inn Express 41 Dock St Dundee City DD1 3DR Tel: +44 (0)1382 314330 Email: [email protected] Email: [email protected] www.holidayinnexpressdundee.com Taxi Service Teletaxis: +44 (0)1382 825825 Dundee Information Centre Discovery Point, Riverside Drive, Dundee, DD1 4XA Tel: +44 (1382) 527527


Poster Session Monday 19.30 – 22.00

Invercarse Hotel, Ballroom P1 Maria Concilio “EPR studies of the conformations and dynamics of the protein kinase activation loop” P2 Beate Sudy “High pressure chemistry: electron transfer in ionic liquids measured by Electron Spin Resonance Spectroscopy” P3 Agnieszka Adamska-Venkatesh “Artificially maturated [FeFe] hydrogenase from C.reinhardtii: HYSCORE and ENDOR study of a non-natural H-cluster” P4 Tomas Mazur “NOx reduction with hydrocarbons on nickel metallozeolite investigated with CW-EPR and HYSCORE spectroscopy and DFT modelling” P5 Burkhard Endeward “PELDOR on Trimeric Betaine Symporter BetP” P6 Stacey Bell “Site Directed Spin Labelling of Bio-Macromolecular Complexes: Cysteine Mutagenesis VS Genetic Code Expansion” P7 Takeji Takui “A ferroelectric ordered state associated with a synchronised proton-electron transfer in mixed-valence Rhenium (III)-Rhenium (IV) complexes as studied by single-crystal ESR spectroscopy and quantum chemical calculations “ P8 Satoru Yamamoto “A pulse sequence study for adiabatic quantum computations in molecular spin quantum computers” P9 Ben Breeze “Rapid scan electron paramagnetic resonance” P10 Naitik Pajwani “Optically Generated Molecular Spin States as Qubits” P11 Claudio Vallotto “Kinetics of polarization of NV−centres in diamond” P12 Angeliki Giannoulis “Metal-nitroxide systems studied with PELDOR at X-band” P13 Silva Valera “PELDOR distance measurements: quantification of artefacts in multi-spin systems” P14 Graham Heaven “Studying the conformational dynamics of HD-PTP by site-directed spin labelling and double electron-electron resonance” P15 Helen Williams “The use of EPR Spectroscopy as a Predictive Tool for Pharmaceutical Formulation Development” P16 Matthew Dale “GPa uniaxial stress of single crystal samples” P17 Sergey Nikolskiy “Spin probing of the fast protonation reactions with semiquinone radicals” P18 Claire Motion “Quantifying the sensitivity of HiPER, the W-Band High Power Pulsed Spectrometer” P19 Michael Stevens “An investigation into the suitability of Rx as a spin label for orientation studies using W-band pulsed electron paramagnetic resonance (PELDOR)”


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P20 Hassane El Mkami “Deuteration impact on the electron spin-echo (ESE) decay of double spin labelled proteins” P21 Christo Pliotas “PELDOR on highly-symmetric multimeric membrane proteins” P22 Marco Albertini “Water mediated triplet-triplet energy transfer: a common feature of the photoprotective site indifferent peridinin-chlorophyll-proteins” P23 Christopher Engelhard “Biophysical, mutational and functional investigation of the chromo-phore-binding pocket of light-oxygen-voltage photoreceptors” P24 Stephen Hogg “Electrically detected magnetic resonance (EDMR) of a-Si:H, toward possible EDMR standard samples” P25 David Finch “EPR of Fe3+ centres in SrTiO3” P26 Diana Aruxandei “Structural conformations of XPD and XPB helicases studied by PELDOR” P27 Stuart Thomson “Electrically detected magnetic resonance of MEH-PPV:PCBM solar cell devices” P28 James Walsh “Magnetostructural trends in water-bridged dinickel complexes” P29 “Stable, Paramagnetic Flavin Model Identified via its Magnetic Nuclei Using Pulsed EPR “ P30 “EPSRC National EPR Research Facility & Service” P31 “How sensitive is HIPER for PELDOR” P32 “Accurate Experimental Characterisation of Spin Label Distributions in Symmetric Multi-Spin Systems – using the MscS channel protein as an exemplar”


ESR Spectroscopy Group Committee The ESR Spectroscopy Group is organised with the aid of a committee of group members, with a Chairman, Secretary and Treasurer. Members serve on the Committee for three years. The Chairman is elected for three years, the Secretary for five years. The Committee often has an international member representing EPR practitioners outside the UK, a representative of one of the spectrometer manufacturers, and a local organiser for the current conference. The Committee Chairman Dr Graham Smith University of St Andrews Secretary Prof Eric McInnes University of Manchester Treasurer Dr Fraser MacMillan University of East Anglia International Representative Prof Gunnar Jeschke

ETH Zurich Web Master Dr Ilya Kuprov

University of Southampton Industry Representative Dr Stephen Brookes

JEOL UK Ltd Committee Member Dr Janet Lovett

University of Edinburgh Committee Member Dr Chris Kay

University College London Committee Member Dr Arzhang Ardavan

University of Oxford

! ! !!

! The 47th International Meeting of the ESR Spectroscopy Group, Dundee 2014!!

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With thanks to our sponsors !

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Delegate List 2014

First Name Last Name e-‐mail Affiliation Maya Abou Fadel maya.abou-‐‑[email protected]‐‑lille1.fr Universite Lille Katrin Ackermann ka44@st-‐‑andrews.ac.uk University of St Andrews Agnieszka Adamska-‐‑

Venkatesh [email protected] Max Planck Institute

Marco Albertini [email protected] University of Padua Simon Ansbro [email protected] The University of

Manchester Amgalanbaatar Baldansuren [email protected] The University of

Manchester Jan Behrends j.behrends@fu-‐‑berlin.de Freie Universität Berlin Stacey Bell sb258@st-‐‑andrews.ac.uk University of St Andrews Aharon Blank [email protected] Israel Institute of

Technology Bela Bode beb2@st-‐‑andrews.ac.uk University of St Andrews Christoph Boehme [email protected] University of Utah David Bolton drb4@st-‐‑andrews.ac.uk University of St Andrews Alice Bowen [email protected] Goethe University,

Frankfurt Ben Breeze [email protected] University of Warwick R David Britt [email protected] University of California,

Davis Steve Brookes [email protected] JEOL UK Goetz Bucher [email protected] University of Glasgow Liliya Bui [email protected] Adani David Cafiso [email protected] University of Virginia David Clapton [email protected] Oxford Instruments Jonathan Cole [email protected] Cryogenics Ltd David Collison [email protected] The University of

Manchester Maria Grazia Concilio [email protected] The University of

Manchester Diana Constantinescu

Aruxandei dca2@st-‐‑andrews.ac.uk University of St. Andrews

David Cross cross@rototec-‐‑spintec.com Rototec-‐‑Spintec Matthew Dale [email protected] University of Warwick Gareth Eaton [email protected] University of Denver Sandra Eaton [email protected] University of Denver Hassane EL Mkami hem2@st-‐‑andrews.ac.uk University of St-‐‑Andrews Adam El-‐‑qmache [email protected] University of Dundee Burkhard Endeward [email protected]‐‑frankfurt.de Goethe University Christopher Engelhard christopher.engelhard@fu-‐‑berlin.de Freie Universität Berlin Gail Fanucci [email protected];[email protected] University of Florida Alistair Fielding [email protected] The University of

Manchester Angelo Frangeskou [email protected] University of Warwick Luca Garbuio [email protected] ETH Zurich


23

First Name Last Name e-‐mail Affiliation Andrew Gibbs [email protected] Bruker UK Limited Guenter Grampp [email protected] Graz University of

Technology Edgar Groenen [email protected] Leiden University Renny Hall [email protected] Hall Scientific Limited Graham Heaven [email protected] The University of

Manchester Arthur Heiss [email protected] Bruker Biospin Corp. Graham Hobbs Rototec-‐‑Spintec Ltd Peter Hoefer Peter.Hoefer@bruker-‐‑biospin.de Bruker BioSpin GmbH Stephen Hogg [email protected] University of Dundee Michael Hollas [email protected] The University of

Manchester Robert Hunter rih1@st-‐‑andrews.ac.uk University of St Andrews Gunnar Jeschke [email protected] ETH Zurich Paul Jonsen [email protected] TalaveraScience Chris Kay [email protected] University College London David Keeble [email protected] University of Dundee Thomas Keevers [email protected] University of New South

Wales Johann Klare [email protected] University of Osnabrück Daniel Klose [email protected] University of Osnabrück Eline Koers [email protected] Utrecht University Ilya Kuprov [email protected] University of Southampton Brendon Lovett bwl4@st-‐‑andrews.ac.uk University of St Andrews Stephen Lyon [email protected] Princeton University Fraser MacMillan [email protected] University of East Anglia Tomasz Mazur [email protected] Jagiellonian University Eric McInnes [email protected] The University of

Manchester Johannes McKay jem74@st-‐‑andrews.ac.uk University of St Andrews Peter Meadows [email protected] JEOL UK Gavin Morley [email protected] University of Warwick Mohamed Morsy [email protected] King Fahd University of

Petroleum & Minerals Claire Motion clm69@st-‐‑andrews.ac.uk University of St Andrews Sinead Mottishaw s.m-‐‑[email protected] University of Warwick Will Myers [email protected] University of Oxford Shigeaki Nakazawa s-‐‑[email protected]‐‑cu.ac.jp Osaka City University Mark Newton [email protected] University of Warwick David Norman [email protected] University of Dundee Vasily Oganesyan [email protected] University of East Anglia Tom Owen-‐‑Hughes [email protected] University of Dundee Naitik Panjwani [email protected] University College London Katharina Pirker [email protected] University of Natural

Resources and Life Sciences, Vienna

Christos Pliotas c.pliotas@st-‐‑andrews.ac.uk University of St Andrews


First Name Last Name e-‐mail Affiliation Daniel Sells [email protected] The University of

Manchester Graham Smith gms@st-‐‑and.ac.uk University of St Andrews Michael Stevens [email protected] University of Dundee Beate Sudy [email protected] Graz University of

Technolgy Dimitri Svistunenko [email protected] University of Essex Claudia Tait [email protected] University of Oxford Takeji Takui [email protected]‐‑cu.ac.jp Osaka City University Mika Tamski [email protected] University of Warwick Anton Tcholakov [email protected] University of Warwick Christian Teutloff christian.teutloff@fu-‐‑berlin.de Freie Universität Berlin Stuart Thomson sajt@st-‐‑andrews.ac.uk University of St Andrews Christiane Timmel [email protected] University of Oxford Silvia Valera sv22@st-‐‑andrews.ac.uk University of St Andrews Claudio Vallotto [email protected] University of Warwick Sabine Van Doorslaer [email protected] University of Antwerp James Walsh [email protected] The University of

Manchester John Walton jcw@st-‐‑and.ac.uk University of St Andrews Richard Ward rw60@st-‐‑andrews.ac.uk University of St Andrews Chris Wedge [email protected] University of Warwick Helen Williams [email protected] AstraZeneca Jörg Wrachtrup [email protected]‐‑stuttgart.de University of Stuttgart Satoru Yamamoto satoru-‐‑[email protected]‐‑cu.ac.jp Osaka City University Peter Heathcote [email protected] Queen Mary University of

London

PELDOR measurements as a means to address structural puzzles in chromatin

C. M. Hammond1, R. Sundaramoorthy1, A. Bowman, A. Stirling1, N. Weichens1, E.Garcia-Wilson1, W. Shang2, H. El-Mkami3, D. I. Svergun2, D.G. Norman1 and T. Owen-Hughes1.

1College of Life Sciences, University of Dundee, UK.2European Molecular Biology Laboratory, Hamburg Outstation, Germany. 3School of Physics and Astronomy, University of St Andrews, UK.

The genomic DNA of eukaryotes is largely associated with proteins to form chromatin. The fundamental subunit of chromatin in the nucleosome which consists of 147bp of DNA wrapped around eight small basic histone proteins. The organisation of chromatin is exploited as a means of regulating access to the underlying genetic information. To achieve this, several classes of protein based molecular machine are used reconfigure the organisation of nucleosomes. To understand how these proteins function, it is important to understand at a structural level how they interact with chromatin. Crystallisation, of such dynamic complexes has proven difficult. As a result we have focused on the adoption of PELDOR measurements to orient domains of known structure with respect to each other. Progress in applying this approach together with other complimentary methods to study histone chaperones and ATP-dependent chromatin remodelling enzymes will be presented.

Figure 1. A tetramer of the histone chaperone Vps75 indicating the positions of engineered cysteine residues used as sites used for site specific attachment of a nitroxyl reporter (MTSL) to enable PELDOR measurements. Labelling of a single site (such as K117) on one chain results in three different interactions within the tetramer. Use of a bi-functional spin label that cross-links between two polypeptides (Y35) provides a simpler single distance distribution within the tetramer.

09.00 – 09.40 K1 Tom Owen-HughesMonday 7 April

Antisymmetric exchange effects in transition ion clusters

E.J.L. McInnes1 1EPSRC National EPR Facility, School of Chemistry and Photon Science Institute, The University of Manchester, UK.

The magnetic anisotropy in transition ion clusters is of fundamental importance in areas such as molecular magnetism through to the characterisation of metalloenzyme active sites. When the ground state can be described by a total electron spin S > !, arising from dominant isotropic exchange interactions, the magnetic anisotropy tends to be dominated by the zero-field splitting (ZFS) of the of the (2S+1)- fold multiplet. This in turn is generally assumed to be dominated by the projection of the local ZFSs of the metal ions.[1] When the local spins are s = ! (and hence have no ZFS) or when they are intrinsically isotropic, such as the 6S MnII ion, it is well understood that the anisotropic component of the exchange can be the main contribution to the ZFS. In contrast, the general significance of the antisymmetric exchange (ASE; also known as the Dzyaloshinski-Moriya exhange) on S > ! states is not so clear. Previous work on ASE inmolecular species has focussed on the symmetry breaking effect on the degenerate s = ! states of spin frustrated systems.[2] In this work we introduce an example where ASE interactions can explain very large ZFSs found in some heterometallic clusters. For example, the S = 5/2 ground state of a Ru2Mn cluster has an axial ZFS of D = 3 cm-1 (Figure 1) which we can explain via ASE effects and where the alternative explanation is an absurdly high local ZFS at MnII which can be ruled out by comparison with the analogous Fe2Mn compound.

This work is supported by the EPSRC. [1] A. Bencini and D. Gatteschi, EPR of Exchange Coupled Systems, Springer-Verlag, Berlin, 1990. [2] for a recent review see: R. Bo!a and R. Herchel, Coord. Chem. Rev. 2010, 254, 2973. Figure 1. (a) 4, (b) 220 and (c) 330 GHz EPR spectra of [Ru2MnO(tBuCO2)6(py)3].Experimental (black) and simulations based on an ASE model (red

09.40 – 10.00 O1 Eric McInnes Monday 7 April

EPR Inquisition of Radicals Released from Oxime Derivatives

John C. Walton University of St. Andrews, EaStCHEM School of Chemistry, St. Andrews, Fife, KY16 9ST.

The prospect for chemistry based around N- and O-centered radicals is very favorable because of the importance of heterocycles as biologically active materials. We investigated a suite of oxime carbonyls, containing the C=N-OC(=O)-Z structural unit, that gave access to a sizeable corpus of useful and esoteric radicals spanning C-, N- and O-centered types. On UV irradiation in solution good quality 9 GHz isotropic EPR spectra were obtained from most members of the suite. The spectra enabled us to study the structures, reaction channels and kinetics, initially of iminyl radicals [Im• = ArCR=N•] and carbamoyl radicals [R2NC•(=O)] derived from oxime esters and oxime oxalate amides respectively [1,2].

Recently we found that oxime carbonates 1 release a pair of iminyl and alkoxycarbonyloxyl radicals on photolysis. The latter species have rarely been studied. An EPR examination of their dissociation to alkoxyls (R1O•) and CO2 and their cyclisations onto alkene and aromatic acceptors will be described [3].

A set of oxime carbamates 2 was also examined and found to release iminyl and hitherto unknown carbamoyloxyl radicals [4]. It was thought the lifetimes of the latter fragile species would be too short for observation. DFT computations predicted that CO2 extrusion would become slower across the series MeCH2CO2• to EtNHCO2• to EtOCO2•. Furthermore, CO2 loss was computed to be slower for RNHCO2• than for R2NCO2• such that the former might have sufficient structural integrity for spectroscopic detection. An EPR investigation testing these predictions will be presented.

[1]. G. A. DiLabio, K. U. Ingold, M. D. Roydhouse and J. C. Walton, Org. Lett. 2004, 6, 4319-4322. [2]. F. Portela-Cubillo, R. Alonso-Ruiz, D. Sampedro and J. C. Walton, J. Phys. Chem. A 2009, 113, 10005–10012. [3]. R. T. McBurney, A. Eisenschmidt, A. M. Z. Slawin and J. C. Walton, Chem. Sci. 2013, 4, 2028-2035. [4]. R. T. McBurney and J. C. Walton, J. Am. Chem. Soc. 2013, 135, 7349-7354.

10.00 – 10.20 O2 John Walton Monday 7 April

New Developments in Ultra-Wideband EPR

A. Doll, S. Pribitzer, G. Jeschke

ETH Zürich, Lab. Phys. Chem, Switzerland.

Modern arbitrary waveform generators (AWGs) provide microwave (mw) bandwidths exceeding the bandwidth of other components of a pulse EPR spectrometer, most notably the resonator. By interfacing a 12 GS/s AWG to a commercial X-band EPR spectrometer, we had previously shown that in adiabatic and fast passage experiments, resonator bandwidth limitations can be overcome by adapting the instantaneous rate of the frequency sweep to the experimentally determined resonator profile [1].

Here we report on an application to sensitivity enhancement for Gd(III)-Gd(III) DEER distance measurements at Q-band frequencies, on chirp echo experiments with a home-built coherent ultra-wideband X-band EPR spectrometer, and on the Matlab library SPIDYAN for simulating experiments with ultra-wideband arbitrary waveform excitation. In conventional Gd(III)-Gd(III) DEER, modulation depths are small even with a high-power Q-band spectrometer, since the excitation bandwidth of full-power monochromatic rectangular mw pulses is much smaller than the spectral width of even the central transition of this S = 7/2 system. A 64 ns long chirp pump pulse with a bandwidth of 450 MHz leads to twofold modulation depth enhancement, without compromising spectral purity of the dipolar evolution in the distance range of interest. Pre-polarization pulses, nicknamed 'bulldozers', allow for transferring thermal spin polarization from the zero-field splitting satellite transitions to the central transition, which leads to another twofold sensitivity enhancement.

Magnetization from all spin packets can be refocused by a primary echo with two chirp pulses, if the refocusing pulse has half the duration of the first excitation pulse [2]. This scheme is shown to allow for Fourier-transform EPR spectroscopy for nitroxides in the solid-state.

Simulation of spin dynamics for such experiments is complicated by the fact that the excitation wave is no longer time-independent in a rotating frame. Computationally efficient simulation schemes are introduced and illustrated on the example of optimizing the polarization bulldozer.

This work is supported by ETHIIRA grant ETH-23.01 11-2 and DFG SPP 1601, grant JE 246/5-1.

[1] A. Doll, S. Pribitzer, R. Tschaggelar, G. Jeschke, Adiabatic and Fast Passage Ultra-Wideband Inversion in Pulsed EPR, J. Magn. Reson. 2013 (230) 27-39.

[2] J.M. Böhlen, M. Rey, G. Bodenhausen, Refocusing with chirped pulses for broadband excitation without phase dispersion, J. Magn. Reson. 1989 (84) 191-197.

11.00 – 11.30 I1 Gunnar Jeschke Monday 7 April

Rapid-Scan EPR and EPR imaging

G. R. Eaton, S. S. Eaton, Z. Yu, J. R Biller, M. Tseitlin, R. W. Quine, G. A Rinard Department of Chemistry and Biochemistry and School of Engineering and Computer Science, University of Denver, Denver, Colorado 80210, USA.

In rapid scans, unlike conventional CW EPR, phase sensitive detection at a magnetic field modulation frequency is not used. Instead, the absorption and dispersion signals are recorded by direct detection with a double balanced mixer. Rapid scans and data analysis permit spectral acquisition with lineshapes that are not modulation broadened. Substantially improved signal-to-noise ratio (S/N) relative to CW spectroscopy has been demonstrated for samples ranging from nitroxides [1] and spin-trapped radicals [2] in fluid solution to paramagnetic centers in solids [3].

The widest rapid-scan spectra that we had previously reported were the 55 G scans of spin-trapped superoxide at X-band [2]. We now report that our technology can be extended to perform 165 G wide sinusoidal scans, which are sufficient to encompass the full spectrum of an immobilized nitroxide. The S/N for the rapid-scan spectra of the immobilized nitroxides is substantially greater than for CW spectra of the same samples. Application to EPR imaging has additional advantages because the amplitude of the absorption spectrum decreases approximately linearly with magnetic field gradient, unlike the approximately quadratic decrease for the first-derivative spectrum. The combination of rapid scan with improvements in digital electronics provides opportunities to revolutionize the way that EPR will be done in the future.

This work is supported by National Science Foundation grant IDBR 0753018 and National Institutes of Health grant EB000557.

Drug Analysis using Electron

(A). Rapid-scan spectrum, (B) first derivative of rapid scan, and (C) CW spectrum obtained in the same 10 s acquisition time.

11.30 – 11.50 O3 Gareth EatonMonday 7 April

[1] D.G. Mitchell, R.W. Quine, M. Tseitlin, S.S. Eaton, and G.R. Eaton, X-band Rapid-Scan EPR of Nitroxyl Radicals. J. Magn. Reson. 2012 (214) 221-226. [2] D.G. Mitchell, G.M. Rosen, M. Tseitlin, B. Symmes, S.S. Eaton, and G.R. Eaton, Use of Rapid-Scan EPR to Improve Detection Sensitivity for Spin-Trapped Radicals. Biophys. J. 2013 (105) 338 - 342. [3] D.G. Mitchell, M. Tseitlin, R.W. Quine, V. Meyer, M.E. Newton, A. Schnegg, B. George, S.S. Eaton, and G.R. Eaton, X-Band Rapid-scan EPR of Samples with Long Electron Relaxation Times: A Comparison of Continuous Wave, Pulse, and Rapid-scan EPR. Mol. Phys. 2013 (111) 2664 - 2673

Paramagnetic Resonance (EPR) Spectroscopy

MOHAMED A. MORSY Chemistry Department, KFUPM, Dhahran 31261, Saudi Arabia.

Recently, electron paramagnetic resonance spectroscopy was successfully utilized as an analytical tool for the investigation of the free radicals generated in different systems including fermented natural leaves [1-3] degraded plastics [4], irradiated alanine [5]. In this study, electron paramagnetic resonance (EPR) is effectively utilized as an analytical tool for the quantitative assay of ketoconazole (KTZ) in drug formulations. The drug was successfully characterized by the prominent signals by two radical species produced as a result of its oxidation with 400 "g/mL cerium(IV) in 0.10 mol dm-3 sulfuric acid. The method newly adopted was fully validated following the United States Pharmacopeia (USP) monograph protocol in both the generic and the proprietary forms. The method is very accurate, such that we were able to measure the concentration at confidence levels of 99.9%. It was also found to be suitable for the assay of KTZ in its tablet and cream pharmaceutical preparations, as no interferences were encountered from excipients of the proprietary drugs. High specificity, simplicity, and rapidity are the merits of the present method compared to the previously reported methods.

References [1] Morsy, M. A.; Khaled, M. J. Agric. Food Chem. 2001, 49, 683. [2] Morsy, M. A.; Khaled, M. Spectrochim. Acta, Part A 2002, 58, 1271. [3] Morsy, M. A. Spectros. Int. J. 2002, 16, 371.[4] Morsy, M. A.; Shwehdi, M. H. Specrochim. Acta, Part A 2006, 63, 624. [5] Al-Karmi, A. M.; Morsy, M. A. Radiat. Meas. 2008, 43, 1315.

11.50 – 12.10 O4 Mohamed MorsyMonday 7 April

Frequency Dependence of Electron Spin Lattice Relaxation for Rapidly Tumbling Radicals

S. S. Eaton, G. R. Eaton, J. R Biller, V. Meyer, and H. Elajaili Department of Chemistry and Biochemistry, University of Denver, Denver, Colorado 80210, USA.

Much of the work on electron spin lattice relaxation has focussed on X-band. Distinguishing contributions from relaxation mechanisms is facilitated by varying frequency. In addition, the increasing interest in radicals as spin probes for in vivo experiments motivates studies of the frequency dependence of relaxation in fluid solution. Three classes of radicals are selected for comparison in the rapid tumbling regime: nitroxides [1], 1,4-benzosemiquinones, and triarylmethyl (trityl) radicals [2]. For nitroxides with tumbling correlation times, #R, between 4 and 50 ps T1-1 at 295 K between 250 MHz and 34 GHz is dominated by spin rotation (SR) and modulation of the anisotropy of the nitrogen hyperfine splitting (END). The contribution from spin rotation is independent of frequency and increases as #R decreases. The contribution from the END process increases at frequencies below 34 GHz. Except for the fastest tumbling nitroxides, T1-1 is larger at lower frequencies. For semiquinones T1-1 increases as frequency is decreased from 9 GHz to 250 MHz in proton-containing solvents, but not in deuterated solvents. The characteristic time for the dynamic process that dominates the relaxation is approximately equal to the tumbling correlation time so the process is attributed to motional averaging of dipolar interaction with solvent nuclei. For trityls the tumbling correlation time at 250 MHz is approximately equal to the proton Larmor frequency and enhanced spin lattice relaxation is attributed to modulation of both intramolecular and intermolecular electron-proton dipolar interaction [2]. Thus, either due to modulation of nitrogen hyperfine anisotropy for nitroxides or modulation of intramolecular or intermolecular electron-proton dipolar interactions for semiquinones or trityls, T1-1 in the rapid tumbling regime is larger at lower frequencies than at X-band.

This work is supported in part by National Institutes of Health grants P41 EB002034 and EB000557.

[1] J.R. Biller, H. Elajaili, V. Meyer, G.M. Rosen, S.S. Eaton, and G.R. Eaton, Electron Spin Lattice Relaxation Mechanisms of Rapidly-Tumbling Nitroxide Radicals. J. Magn. Reson. 2013 (236) 47 - 56. [2] R. Owenius, G.R. Eaton, and S.S. Eaton, Frequency (250 MHz to 9.2 GHz) and Viscosity Dependence of Electron Spin Relaxation of Triarylmethyl Radicals at Room Temperature. J. Magn. Res. 2005 (172) 168-175.

12.10 – 12.30 O5 Sandra Eaton Monday 7 April

Chemometrics tools for the separation of chemical contributions in EPR spectroscopy

M. Abou Fadel, H. Vezin, L. Duponchel Université Lille1 Sciences et Technologies, Laboratoire de Spectrochimie Infrarouge et Raman (LASIR-UMR 8516) Bât. C5 59655 Villeneuve d’Ascq Cedex, France. EPR spectra are often difficult to interpret and analyze due to the high degree of super-position of spectral contributions of various paramagnetic ions and radicals. The chal-lenge to resolve the multicomponent systems obtained from EPR spectroscopy is equal-ly present in a series of spectra with concentration variations as well as data evolving in time (kinetics) and data evolving in space (imaging). The aim of this study is to show, for the first time, feasible and powerful chemometrics tools applied on such complex data to identify all the pure spectral contributions and their corresponding concentration profiles. Chemometrics is a chemical discipline that uses mathematics, statistics, and formal logic to design or select optimal experimental procedures. It is used to explore the chemical data in order to provide maximum relevant information and knowledge about the chemical systems. Multivariate curve resolution-Alternating Least Squares (MCR-ALS) belongs to the class of self-modeling algorithms [1-3]. It is a potent and wide-spread chemometrics method based on factor analysis that unravels the pure contribu-tions of all the species in the spectroscopic dataset i.e their concentration profiles and their corresponding pure spectra without requiring information about the underlying physicochemical system. MCR proved to resolve, successfully, problems associated to the presence of high level of overlapping and unknown systems present in EPR spectra. The attained results of MCR-ALS treatment on datasets that evolves in time, such as the reaction of benzo-coumarin with sodium hydroxide will be presented. Pure spectra and their correspond-ing time profiles of the radicals formed through the reaction are easily separated. In ad-dition, we will present results achieved by the application of MCR-ALS on EPR data evolving in space, as an example, image of CaF2 with crystal defects. Identification of the different defects present in the sample will be shown by map distributions and their spectral contributions.

[1] R. Tauler, Multivariate curve resolution applied to second order data, Chemometrics and Intelligent Laboratory Systems, 1995 (30) 133-146. [2] A. de Juan, R. Tauler, Chemometrics applied to unravel multicomponent processes and mixtures - Revisiting latest trends in multivariate resolution, Analytica Chimica Acta, 2003 (500) 195-210. [3] S. Piqueras, L. Duponchel, M. Offroy, F. Jamme, R. Tauler, A. de Juan, Chemometric Strategies To Unmix Information and Increase the Spatial Description of Hyperspectral Images: A Single-Cell Case Study, Analytical Chemistry, 2013 (85) 6303-6311.

14.00 – 14.20 O6J Maya Abou Fadel Monday 7 April

Gd(III) – nitroxide DEER on proteins: chemo-selective labelling, technique optimization and combination with paramagnetic NMR.

L. Garbuio, Laboratory of Physical Chemistry, ETH Zurich, Switzerland.

DEER-based distance measurements between a Gd(III) ion and a nitroxide radical were proposed, demonstrated on model systems [1] and analysed theoretically over the last three years. Notwithstanding, to fully exploit the advantages of this approach in studies of bio-macromolecules and their complexes, one requires procedures for chemo-selective attachment of dissimilar spin labels. Furthermore, these types of tags are employed in paramagnetic NMR and it is therefore natural to combine the two techniques in structural investigations. In this work we systematically applied the Gd(III) – nitroxide DEER method and analysed its performance on two proteins. We report two different schemes of site-directed chemo-selective labelling, one for a monomeric protein and one for an enzyme-inhibitor system. We take advantage of the unnatural amino acid technology and test a new type of conformationally rigid lanthanide tag. The spectroscopical properties of two commercially available Gd(III) spin labels are looked into and the Gd(III)-nitroxide DEER sequence is optimized for the best sensitivity at specific Q-band conditions (high power setup and broad band resonator). [2]

Paramagnetic relaxation enhancement and pseudo contact shift NMR are combined with DEER. [3a] Correspondences between NMR and EPR constraints are analysed and a guideline for a joint use of those data is presented. Noteworthy, we show that at Q band, orientation selection can be sufficient to extract the nitroxide orientation with respect to the protein. We subsequently apply the DEER method to an interesting case of study, the PolyProline II (PPII), a helical structure widely exploited as molecular scaffold. Here Gd(III) - nitroxide and nitroxide – nitroxide DEER provide complementary information that shed light on the flexibility of PPII peptides. [3b] These examples reveal that Gd(III)-nitroxide DEER is a reliable and versatile tool in studies of biomacromolecules. In particular, the benefits of extended spectroscopic information content and ease of combination with further techniques, such as paramagnetic NMR, may render Gd(III) – nitroxide DEER the preferable method in many applications.

This work is supported by SNF grant no. 200021_121579.

[1] P. Lueders, G. Jeschke, M. Yulikov, Double electron!electron resonance measured between Gd3+ ions and nitroxide radicals, J. Phys. Chem. Lett., 2011 (2) 604!609. [2] L. Garbuio, E. Bordignon, E. K. Brooks, W. L. Hubbell, G. Jeschke, M. Yulikov,Orthogonal spin labeling and Gd(III)!nitroxide distance measurements on bacteriophage T4-lysozyme, J. Phys. Chem. B, 2013 (117) 3145-3153. [3] (a) L. Garbuio, K. Zimmermann, D. Häussinger, G. Jeschke, M. Yulikov. [b] L. Garbuio, L. Ziegler, B. Lewandowski, P. Wilhelm, H. Wennemers, G. Jeschke, M. Yulikov, Manuscripts in preparation.

14.20 – 14.40 O7J Luca Garbuio Monday 7 April

Spectroscopic Investigation of Spin-Dependent Optoelectronic Path-ways in Organic Devices

T. L. Keevers1, A. Danos2, W. Baker1, H. Malissa3, M. Kavand3, C. Boehme3, D. R. McCamey1 1 School of Physics, University of New South Wales, Sydney NSW 2052, Australia 2 School of Chemistry, University of New South Wales, Sydney NSW 2052, Australia 3 Department of Physics and Astronomy, University of Utah, Salt Lake City Utah 84112, USA

The low cost and flexibility of organic polymers makes them ideal for a range of interesting optoelectronic applications. De-vice optimization may be assist-ed through microscopic under-standing of spin-dependent pathways. Due to the low spin volumes present in these devices, exploration of spin-dependent pathways through magnetic res-onance generally needs to be coupled with electrical or optical detection for sufficient sensitivi-ty [1], and to allow the discrimi-nation of the paramagnetic states which affect the optoelectronic pathways. The low dielectric constant and highly disordered structure of organic semiconductors may lead to the formation of weakly spin-interacting, coulombically bound polaron pairs. These states can be accessed through resonant changes in luminosity or conduc-tivity due to overall changes in spin-dependent recombination [2]. We use these methods to investigate the spin relaxation and charge transport rates in various organic materials. Polaron pair hopping is significantly slower than its free car-rier counterpart, suggesting Coulombic interactions may inhibit transport [3]. We develop a framework for the interpretation and prediction of electrically-detected signals in the weakly interacting pair limit and show that simultaneous excitation of the electron and hole (“spin beating”) may significantly influence complex pulse sequences.

[1] Lupton, J. M., et al., ChemPhysChem 11, 3040-3058 (2010) [2] McCamey, D. R., et al., Nature Materials 7, 723-728 (2008) [3] Baker, W. J., et al., Phys. Rev. Lett. 108, 267601 (2012)

Figure 1. Polaron pairs may spin-dependently dissociate into free polarons or form excitons and recombine. We can manipulate these rates through resonant excitation.

14.40 – 15.00 O8J Thomas Keevers Monday 7 April

Tracing the transient conformational signal in bacterial phototaxis using SDSL-EPR spectroscopy

D. Klose1, P.S. Orekhov2, I. Orban-Glass1, C. Rickert1, A.Y. Mulkidjanian1, K.V. Shai-tan2, M. Engelhard3, J.P. Klare1 and H.-J. Steinhoff1 1University of Osnabrück, Department of Physics, Osnabrück, Germany. 2Moscow State University, School of Biology, Moscow, Russia. 3Max-Planck-Institute for Molecular Physiology, Dortmund, Germany.

In Natronomonas pharaonis a sensory rhodopsin II – transducer complex (SRII/HtrII) mediates negative phototaxis.1 Upon photo-activation a light-induced outward move-ment of receptor helix F induces a shift and rotation of the coupled transducer helix TM2.1 This signal propagates along the coiled coil transducer HtrII to the distal kinase CheA via a yet unknown mechanism.

For the adjacent HAMP domain, a widely abundant signaling module, several mechanisms were suggested, all comprising two distinct conforma-tional states. These can be observed by two-component cw-EPR spectra at ambient temperatures existing in a thermodynamic equilibrium which can be driven by salt-, temperature- and pH-changes.

To trace the conformational signal and it’s propagation throughout the elon-gated transducer, we applied cw- and pulse-EPR spectroscopy in conjunc-tion with nitroxide spin labeling. We follow transient changes by time-resolved cw-EPR spectroscopy and compare the resulting spectral changes to difference spectra corresponding to the above shifts in the thermodynamic equilibrium. The light-driven conformational changes are in agreement with a shift towards a more compact state of the HAMP domain.

In large scale coarse grain molecular dynamics simulations of the SRII/HtrII trimers-of-dimers we observe the activation of the complex. In conjunction with experimental data, this leads to a model (Fig. 1) for signal propagation by dynamic allostery along the ex-tended coiled coil transducer HtrII.

[1] J.P. Klare, Eur. J. Cell. Biol. 2011 (90) 731-739.

15.00 – 15.20 O9J Daniel Klose Monday 7 April

Figure 1. Model suggested for the signaling mechanism of SRII/HtrII trimer-of-dimer complexes.

NMR-based Structural Biology enhanced by Dynamic Nuclear Polarization at high magnetic field

Eline J. Koers1, Elwin A. W. van der Cruijsen1, Melanie Rosay2, Markus Weingarth1, Alexander Prokofyev13, Claire Sauvée4, Olivier Ouari4, Olaf Pongs3, Paul Tordo4, Werner E. Maas1, Marc Baldus1 1Bijvoet Center for Biomolecular Research, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands, 2Bruker BioSpin Corporation, 15 Fortune Drive, Billerica MA 01821, USA, 3Saarland University, Faculty of Medicine, Department of Physiology, Building 59, 66421 Homburg, Germany, 4Aix-Marseille Université, CNRS, ICR UMR 7273, 13397 Marseille, France.

Dynamic Nuclear Polarization (DNP) has become a powerful method to enhance spectroscopic sensitivity in the context of Magnetic Resonance Imaging (MRI) and Nuclear Magnetic Resonance (NMR) spectroscopy [1]. We show that the combination of high field DNP (800 MHz/527 GHz) with Magic Angle Spinning (MAS) solid-state NMR can significantly enhance spectral resolution and allows exploitation of the paramagnetic relaxation properties of DNP polarizing agents as direct structural probes. It also provides a new tool to investigate paramagnet-nucleus interactions.

Applied to a membrane-embedded K+ channel KcsA, this approach allowed us to refine the membrane-embedded channel structure and revealed conformational substates that are present during two different stages of the channel gating cycle. High-field DNP thus offers atomic insight into the role of molecular plasticity during the course of biomolecular function in a complex cellular environment.

This work was supported by NWO (grants 700.11.344 and 700.58.102 to MB), DFG (Po137, 40-1& 41-1) and NIH (NIH/NIGNS grant GM087519).

[1] RG Griffin, TF Prisner, Phys. Chem. Chem. Phys. High field dynamic nuclear polarization—the renaissance 2010 (12) 5737.

[2] C Ader, R Schneider, S Hornig, P Velisetty, EM Wilson, A Lange, K Giller, I Ohmert, M-F Martin-Eauclaire, D Trauner, S Becker, O Pongs, M Baldus, A structural link between inactivation and block of a K+ channel.Nat Struct Mol Biol 2008 (15) 605-612

Figure 1. DNP at 100 K. on KcsA revealed additional substates of the protein as well as local dynamics in the selectivity filter.

16.00 – 16.20 O10J Eline Koers Monday 7 April

Orientation selective PELDOR measurements of the RX spin label J.McKay1, M. Stevens2, H. El-Mkami1, R. Hunter1, D. Bolton1, P. Cruickshank1, D. Norman2, G. Smith1 1 School of Physics and Astronomy, University of St Andrews, St Andrews, UK 2 School of Life Sciences, University of Dundee, Dundee, UK It has been shown that it is possible to use high-field EPR (Electron Paramagnetic Resonance) measurements to obtain accurate long range angular and distance constraints which could be used to build structural models of large biomolecular structures. By using the conformationally constrained nitroxide side chain RX [1] as a spin label it is possible to label secondary structure reliably such that the side chain conformation can be correlated to the underlying structure. In this paper we describe a reliable library method for measuring and extracting the relative orientation and distance between pairs of RX spin labels using PELDOR (Pulsed Electron-Electron Double Resonance) at W-band using the HiPER spectrometer at St Andrews [2]. As part of collaboration with Nucleic Acids Research Group, University of Dundee samples have been prepared with the RX side chain attached to alpha helix and beta sheet secondary structure. Analysis results for PELDOR measurements of these different pairs of spin labels are presented and compared to existing structural models. A study into the angular resolution of the PELDOR measurements of spin labels with the conformational constraints found in the RX side chain will be presented.

By combining angular and distance constraints derived from conformationally constrained side chains measured with high-field EPR it is hoped that it will be possible to build structural models of large biomolecular systems in a general way. 1. Fleissner, M.R., et al., Structure and dynamics of a conformationally constrained nitroxide side chain and applications in EPR spectroscopy. Proceedings of the National Academy of Sciences, 2011. 2. Cruickshank, P.A.S., et al., A kilowatt pulsed 94 GHz electron paramagnetic resonance spectrometer with high concentration sensitivity, high instantaneous bandwidth, and low dead time. Review of Scientific Instruments, 2009. 80(10): p. 103102.

Figure 1 Nitroxide sidechain RX

16.20 – 16.40 O11J Johannes McKay Monday 7 April

EPR study on triplet state delocalisation in conjugated porphyrin systems

Claudia E. Tait‡, Patrik Neuhaus†, Christiane R. Timmel‡, Harry L. Anderson† † Department of Chemistry, University of Oxford, Chemistry Research Laboratory, Mansfield Road, Ox-ford OX1 3TA ‡ Department of Chemistry, University of Oxford, Centre for Advanced Electron Spin Resonance, South Parks Road, Oxford OX1 3QR

Delocalisation of the photoexcited triplet state in a linear conjugated porphyrin dimer has been investigated using time-resolved EPR, ENDOR and HYSCORE at X- and Q-band frequencies. Previous studies on covalently linked porphyrin arrays have concluded that the triplet state remains localised on a single porphyrin unit independently of the linking geometry [1]. Triplet state delocalisation over more than one porphyrin-like unit has so far only been demonstrated in cofacial dimers, most notably in the special pair of a photo-synthetic reaction centre [2].

Time-resolved EPR spectra of the photo-excited triplet states of a porphyrin monomer and the corresponding butadiyne-linked dimer were recorded. The spectra are character-ised by significantly different spin polarisations and an increase of the zero-field split-ting parameter, D, from monomer to dimer. The proton and nitrogen hyperfine interac-tions were determined using 1H Mims ENDOR and 14N HYSCORE; both the proton and nitrogen hyperfine couplings in the dimer are reduced to about half with respect to the monomer (Figure 1), demonstrating delocalisation of the triplet state over both porphy-rin units.

Orientation-selective ENDOR and HYSCORE aided by DFT calculations allowed determination of the orientations of the zero-field splitting tensors in the porphyrin monomer and dimer. The results provide evidence for an oblate-to-prolate spin transition, with reorientation of the direction of largest dipolar interaction from the out-of-plane axis in the monomer to the vector connecting the two porphyrin units in the dimer.

[1] Angiolillo, P. J.; Susumu, K.; Uyeda, H. T.; Lin, V. S.-Y.; Shediac, R.; Therien, M.

16.40 – 17.00 O12J Claudia Tait Monday 7 April

Figure 1. 1H Mims ENDOR spectra re-corded on the porphyrin monomer and dimer at the X canonical field position.

Electrochemical Electron Paramagnetic Resonance utilizing micro-electrodes and loop gap resonators

Mika Tamski1, M. E. Newton1, J. V. Macpherson2 and P. R. Unwin2

Departments of Physics1 and Chemistry2, University of Warwick

EPR can provide valuable information about the radical species generated during electrochemical reactions. When combining electrochemistry with EPR (ECEPR) the focus has often been given to the design of the electrochemical cell to be used with EPR resonators. Loop Gap Resonator (LGR) is a novel EPR resonator structure originally adapted to electrochemical purposes by Allendoerfer et al [1]. The characteristics of LGR allow the study of aqueous or “lossy” samples, where a good EPR sensitivity can be achieved with relatively small sample volumes.

Building on Allendoerfer’s work here we report a new electrochemical cell structure designed to be used with LGR and aqueous solvents in in-situ ECEPR studies. The use of wire electrodes with diameters of tens of micrometres give the cell the benefits generally related to microelectrodes while the length of the electrode guarantees high enough absolute currents for convenient ECEPR studies. The electrochemical performance of the design is discussed and contrasted with COMSOL finite element models, while the EPR performance is demonstrated using Methyl Viologen as a redox mediator.

Support from the EPRSC Integrated Magnetic Resonance Centre for Doctoral Training (www.imr-cdt.ac.uk) is gratefully acknowledged.

[1] R.D. Allendoerfer, W. Froncisz, C. C. Felix, J. S. Hyde, I. Newton, Electrochemical Generation of Free Radicals in an EPR Loop-Gap Resonator, Journal of Magnetic Resonance, 1988 (76) 100-105.

Figure 1. Structure of the newly designed electrochemical EPR cell for aqueous samples showing Working, Reference and Counter Electrodes (WE, RE, CE)

17.00 – 17.20 O13J Mika Tamski Monday 7 April

Pulsed Electrically Detected Magnetic Resonance Spectroscopy of Organic Semiconductors

C. Boehme Department of Physics and Astronomy, University of Utah, Salt Lake City, USA With the emergence of spintronics concepts based on organic semiconductors and re-newed interest in the role of spin for the performance of organic light emitting diodes, transistors, and solar cells, there is much need for an understanding of the fundamental properties of spin-controlled charge carrier processes in organic electronic materials. A direct experimental approach to this is monitoring observables that are controlled by spins while these spins are then manipulated in a well-defined way, e.g. when spin-dependent charge currents are measured while spin states are manipulated coherently with electron paramagnetic resonance (EPR), an experiment called pulsed electrically detected magnetic resonance spectroscopy (pEDMR) [1]. In this presentation, pEDMR spectroscopy on organic semiconductor materials such as $-conjugated polymer and Fullerene based solids will be discussed. Technical require-ments for pEDMR spectroscopy will be described [2] and recent experimental results will be presented [3-5]. PEDMR can resolve the dynamics of conductivity related spin-dependent processes with great sensitivity, even for small-volume thin-film material and device samples and it reveals the nature of these mechanisms. The latter has been a quite controversial topic due to the abundance of different spin-dependent processes that have been hypothesized in the literature [6]. Compared to inductively detected EPR, pEDMR is sensitive to different observables such as spin-permutation symmetry when the Pauli blockade governs a spin-dependent signal. However, we have developed procedures which can map conventional EPR ob-servables (e.g. spin-polarization induced Hahn-echoes) onto pEDMR observables. This allows us to apply for pEDMR spectroscopy many pulse sequences, phase cycling schemes, and double resonance techniques that have been developed for pulsed EPR spectroscopy over the past decades. Consequently, pEDMR can give accurate quantita-tive information about spin-relaxation times, electronic transition times, diffusion pro-cesses, and spin-dephasing times as well as spin interactions, including spin-orbit, spin-dipolar, exchange- and hyperfine couplings.

[1] C. Boehme and K. Lips, Phys. Rev. B 68, 245105 (2003). [2] D. R. McCamey, H. A. Seipel, S. Y. Paik, M. J. Walter, N. J. Borys, J. M. Lupton, and C. Boehme, Nature Materials 7, 723 (2008). [3] D. R. McCamey, K. J. van Schooten, W. J. Baker, S.-Y. Lee, S.-Y. Paik, J. M. Lupton, and C. Boehme, Phys. Rev. Lett. 104, 017601 (2010). [4] W. J. Baker, K. Ambal, D. P. Waters, R. Baarda, H. Morishita, K. van Schooten, D. R. McCamey, J. M. Lupton, and C. Boehme, Nature Commun. 3, 898 (2012). [5] W. J. Baker, T. L. Keevers, J. M. Lupton. D. R. McCamey, and C. Boehme, Phys. Rev. Lett. 108, 267601 (2012). [6] C. Boehme and J. M. Lupton, Nature Nano. 8, 612 (2013).

09.00 – 09.40 K2 Christoph Boehme Tuesday 8 April

High Resolution Microimaging with Pulsed Electrically-Detected Magnetic Resonance

Itai Katz,* Matthias Fehr,# Alexander Schnegg,# Klaus Lips,# and Aharon Blank* *Schulich Faculty of Chemistry, Technion – Israel Institute of Technology, Haifa, 32000 Israel # Helmholtz-Zentrum Berlin für Materialien und Energie, Institut für Silizium- Photovoltaik, Kekuléstr. 5, D-12489 Berlin, Germany

The investigation of paramagnetic species (such as point defects, dopants, and impurities) in semiconductor devices is of significance, as they affect device performance. Conventionally these species are detected and imaged by electron spin resonance (ESR) technique. Many times ESR is not sensitive enough to deal with miniature devices having small number of paramagnetic species and high spatial heterogeneity. This limitation can in principle be overcome by employing a more sensitive method called electrically-detected magnetic resonance (EDMR), which is based on measuring the effect of paramagnetic species on the electric current of the device while inducing electron spin flip transitions. However, up until now, measurement of the current of the device could not reveal the spatial heterogeneity of its paramagnetic species. In this work we show for the first time how to acquire high-resolution microimages of paramagnetic defects in an operating solar cell using EDMR (Fig. 1). The method is based on unique microwave pulse sequence for excitation and detection of the electrical signal under static magnetic field and powerful pulsed magnetic field gradients that spatially encode the electrical current information of the sample. The method developed can be of wide use for the nondestructive three-dimensional inspection of paramagnetic species in a variety of semiconductor devices.

This work was partially supported by grant # G-1032-18.14/2009 from the German- Israeli Foundation (GIF), grant #213/09 from the Israeli Science Foundation, grants #201665 and #309649 from the European Research Council (ERC), and by the Russell Berrie Nanotechnology Institute at the Technion. AS received funding from the German Federal Ministry of Education and Research (BMBF grant #03SF0328).

09.40 – 10.00 O14 Aharon Blank Tuesday 8 April

A ground-state triplet iminonitroxide-nitroxide diradical in magneti-cally diluted single crystal as studied by CW-ESR/pulsed ESR spec-troscopy

S. Nakazawa1,2, M. Kawamori1, K. Sugisaki1, K. Toyota1,2, D. Shiomi1,2, K. Sato1,2, K. Omukai1, T. Furui1, M. Kuratsu1, S. Suzuki1, M. Kozaki1, K. Okada1 and T. Takui1,2 1Graduate School of Science, Osaka City University, Osaka 558-8585, JAPAN 2FIRST-Quantum Information Processing Project, JSPS, Tokyo 101-8430, JAPAN

Recently, the study of quantum computing/quantum information processing (QC/QIP) by pulse ESR techniques hasattracted much attention, being underlain by novel mo-lecular spins and implementation of new pulse ESRtechnology.Extremely stable and highly compact nitoroxide-substituted iminonitroxide 1was synthesized [1], which serves for not only a building block for organic molecular magnetic materials but also an electron spin-qubit for memory devices coupled with qubit systemsfor gate opera-tions of QC/QIP.Triplet diradical 1in the ground state has a large Dvalue (-0.0655 cm-1), the largest among the ground state triplet (S= 1) nitroxide diradicals documented so far. We made magnetically diluted single crystals which are able to serve as the quantum spin memory. Temperature dependence of the Dvalue was observed, which was inter-preted by the change of the molecular structure in the diamagnetic host single crystal with changing temperature. The structuralchange resulting in the modulation of the Dvalue was explained in terms of quantum chemical calculations. During the identification of the magnetic properties of 1in pulse ESR experiments, we observedthe disappearance of the fine-structure ESR signal associated withacata-strophic change of the spin-spin relaxation time at around25K,suggesting the occur-rence ofaphase transition. We alsoobserved double quantum (DQ) transitions in the fine-structure ESR spectra in both organic glassesand the single crystal at low tempera-tures.Two types of the mechanism for the DQ transition have been proposed in the lit-erature [2]. In our case at 50 Kin glasses, the power dependence of the DQ signal is in-dicative of the mechanism of the consecutive absorptionof microwave quanta.Avoiding saturation effects, pulsed ESR spectroscopy was used below 50 K. The power depend-ence ofthe DQ nutation frequency at 10 K also suggested the occurrence of the consec-utiveabsorption. In order to study the DQ mechanism in microsopic terms, the single-crystal ESR spectroscopy of diradical 1 was carried out. The DQ transitions in the single-crystal ESR spectra were identified at low temperatures by using both Q-band CW ESR and pulsed-ESR based nutation spectroscopy. Microscopic origins of the DQ transitions in the present system are proposed.

[1] S. Suzuki, T. Furui, M. Kuratsu, M. Kozaki, D. Shiomi, K. Sato, T. Takui and K. Okada, J. Am. Chem. Soc. 2010 (132) 15908-15910. [2] D. Collison, M. Helliwell, V.M. Jones, F.E. Mabbs, E.J.L. McInnes, P.C. Riedi, G.M. Smith, R.G. Pritchard and W.I. Cross, J. Chem. Soc., Faraday Trans. 1998 (94) 3019-3025

10.00 – 10.20 O15 Shigeaki Nakazawa Tuesday 8 April

Low power high sensitivity pulsed ESR for quantum information experiments

S.A. Lyon

Department of Electrical Engineering, Princeton University, USA.

Measuring spin systems for applications in quantum information poses unique challenges for pulsed-ESR experiments. Systems with very long spin coherence, T2, are crucial, since loss of coherence is a form of error. Isotopically enriched 28Si is an excellent host for long-coherence electron spins, and we have shown T2 ~ 10s in bulk crystals. Very dilute spin systems are required to avoid spin-spin interactions, and in quantum devices the spins usually must reside near a surface where they can be controlled by electrostatic gates. However, that implies that there are very few spins, and thus we must improve sensitivity. In addition, the qubits must be “initialized,” which typically means operating at mK temperatures where the maximum power dissipation is limited to microwatts.

In this talk I will describe recent experiments1 using superconducting Nb coplanar-waveguide (CPW) resonators fabricated on a silicon wafer, together with helium-cooled microwave switches and preamplifiers to measure pulsed-ESR from electrons bound to donor impurities in isotopically enriched 28Si. We obtain single-shot sensitivity to about 107 spins at 1.7 K, which translates to about 104 spins/!Hz with averaging. This single-shot sensitivity is about 5 orders of magnitude better than we have been able to achieve with conventional volume resonators.

Our ability to measure long spin coherence is limited by fluctuations of the magnetic field. These fluctuations typically have approximately a 1/f" power spectrum, with " in the range of 1 to 2. Similar noise levels are seen with both room-temperature resistive magnets and superconducting magnets. I will discuss recent attempts to understand and reduce the effect of this magnetic field noise.

This work was supported in part by the US Army Research Office and by the National Science Foundation.

1. A.J. Sigillito, et al., “Fast, low-power manipulation of spin ensembles in superconducting microresonators,” arxiv:1403.0018.

11.00 – 11.30 I2 Stephen Lyon Tuesday 8 April

Figure 1. Photograph of a Si-sample with 4 capacitively-shorted CPW resonators. The resonators have different lengths, giving different resonant frequencies. The capacitive shorts allow the center conductor of the resonator to be DC-biased. This device is 2mm x 7mm in size.

Towards a Molecular-Magnet based Quantum Computer: Double Electron-Electron Resonance Analysis of Two Qubit Metal-Ring Dimers

A.M. Bowen1, G.A. Timco2, A. Fernandez2, D. Kaminski1, F. Moro2, A.L. Webber1, F. Tuna2, A. Fielding2, C.R. Timmel1, D. Collison2, R.E.P. Winpenny2, E.J.L McInnes2 and A. Ardavan1.

1Centre for Advanced Electron Spin Resonance (CAESR), Department of Physics, University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU. 2National EPR Research Facility, University of Manchester, Alan Turing Building, Oxford Road, Manchester, M13 9PL.

Within the wide array of different systems that have been proposed as the basis for a quantum computer Cr7Ni metal-ring molecular-magnets have shown great promise due to the relative ease with which they can be chemically engineered to change both their magnetic and structural properties. Previous pulsed ESR studies have concentrated on the monomer rings [1]; however, in order to implement complex computational algorithms it is necessary to obtain arrays of coupled qubits in which each qubit can be manipulated independently.

In this study we have investigated two families of Cr7Ni dimers; chemically linked rings [2] and rotaxane threaded rings [3] as potential two qubit systems (see figure). The dipolar coupling between the two rings was measured using Double Electron-Electron Resonance (DEER) at X-band for the molecules in frozen solution at 2.5 K. At this temperature the excited spin states are not significantly populated compared to the S=1/2 ground state. Due to the broad nature of the frozen-solution EPR spectrum, the pulses used in the DEER experiment excite only a small fraction of the spins corresponding to a limited number of orientations of the molecule with respect to the external magnetic field. Orientationally selective analysis of the DEER traces was achieved with reference to the X-ray crystallographic structures and provided an indication of the flexibility of the molecules in frozen solution.

In order to record DEER it is necessary to excite two coupled spins independently. Therefore these spectra indicate that it is possible to use orientational selectivity to manipulate the spin of the two Cr7Ni rings separately. This demonstrates the potential to use arrays of metal-rings as qubits providing an exciting opportunity to build a chemically tuneable quantum computer. [1] A. Ardavan et al., Phys. Rev. Lett., 98, 057201, (2007) and C.J. Wedge et al., Phys. Rev. Lett., 108, 107204, (2012). [2] T.B. Faust et al., Chem. Eur. J., 17, 14020, (2011). [3] S. Piligkos et al., Chem. Eur. J., 15, 3152, (2009).

X-ray structures of a chemically linked Cr7Ni dimer (left, GT201) and rotaxane threaded Cr7Ni dimer (right, AF297) with corresponding orientationally selective DEER traces: blue (raw data), red (filtered to remove 1H-ESEEM) and green (simulated traces).

11.30 – 11.50 O16 Alice BowenTuesday 8 April

NMR-paradigm pulse ESR spectroscopy: Coherent multi-frequency spin manipulation technology for spin-based quantum computers and quantum information processing

Kazunobu Sato1,4, Shigeaki Nakazawa1,4, Satoru Yamamoto1, Ayaka Tanaka1, Tomohiro Yoshino1,4, Kenji Sugisaki1,4, Shinsuke Nishida2,4, Tomoaki Ise1,4, Yasushi Morita2,4, Kazuo Toyota1,4, Daisuke Shiomi1,4, Masahiro Kitagawa3,4 and Takeji Takui 1,4

1Graduate School of Science, Osaka City University, Osaka, Japan 2Graduate School of Science, Osaka University, Toyonaka, Japan 3Graduate School of Engineering Science, Osaka University, Toyonaka, Japan 4FIRST-Quantum Information Processing Project, JSPS, Tokyo, Japan

Considerable research on quantum computing and quantum information processing (QC/QIP) has been achieved from the theoretical side for the last decades. Among physically realized qubits, molecular electron spin qubits have been the latest arrival [1-4], although electron spins in molecular frames have naturally been anticipated as typical matter spin qubits. In quest of ensemble molecular spin qubits from the chemistry and materials science sides, “a” smallest QC has been implemented, in which controlled-NOT gates are for the first time established [4]. Among the essential issues relevant to QC/QIP, all the physical qubits have faced the issues of qubit scalability and quantum error corrections associated with decoherency of qubits. The solution-NMR approach has brought QC down to earth in terms of spin qubit manipulation technology, but suffers from the lack of real entanglement [1,3]. In this context and molecular optimisation, electron spin qubits are promising because they maintain intrinsic high polarisation and play a hyperpolarising role in molecular quantum spin cybernetics.

From the viewpoint of quantum cybernetics, we survey so far established electron/nuclear spin manipulation technology for ensemble molecular spin qubits, in which the electron and nuclear spins play a bus qubit and client ones, respectively [1-4]. In terms of pulse-based microwave spin resonance techniques, the number of available coherent multi-frequencies has been limited and thus far molecular spin qubits haven’t afforded their advantages in the field of QC/QIP. Recent theoretical progress in QC/QIP and quantum cybernetics requires coherent control of multi-frequency electron spin qubits in ensemble, in which electron and spin qubits are equivalently manipulated in a desired manner. Recently, we have established the electron spin manipulation technology with arbitrary wave generators (AWGs), which is based on coherent microwave pulsed multi-frequency resonance techniques for the precise manipulation of molecular spins. This new technology with the AWG apparatus can widely be applicable to various types of pulsed ESR experiments including coherent electron-spin multiple resonance.

[1] R. Rahimi, K. Sato, T. Takui et al., Int. J. Quantum Inf. 2005 (3) 197-204. [2] K. Sato, R. Rahimi, T. Takui et al., Physica E 2007 (40) 363-366. [3] K. Sato, S. Nakazawa, Y. Morita, T. Takui et al., J. Mater. Chem. 2009 (19) 3739-3754. [4] S. Nakazawa, K.Sato, Y. Morita, T.Takui et al., Angew. Chem. Int. Ed. 2012 (51) 9860-9864.

11.50 – 12.10 O17 Takeji Takui Tuesday 8 April

Potential for spin-based information processing in a thin-film molecular semiconductor

Marc Warner1, Salahud Din2, Igor S. Tupitsyn3, Gavin W. Morley1, A. Marshall Stoneham1, Jules A. Gardener2, Zhenlin Wu2, Andrew J. Fisher1, Sandrine Heutz2, Christopher W. M. Kay4 and Gabriel Aeppli1,2 1London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, WC1H 0AH, UK. 2London Centre for Nanotechnology and Department of Materials, Imperial College London, London, SW7 2AZ, UK.3Pacific Institute of Theoretical Physics, University of British Columbia, British Columbia, V6T 1Z1, Canada 4Institute of Structural & Molecular Biology and London Centre for Nanotechnology, University College London, London, WC1E 6BT, UK

Organic semiconductors are studied intensively for applications in electronics and optics, and even spin-based information technology, popularly referred to as spintronics. Fundamental quantities for spintronics are the population relaxation (T1) and phase memory (T2) times: the first measures the lifetime of a classical bit represented as a spin pointing either parallel or antiparallel to an external field, and the second that for a quantum bit.

Here we establish that these times are surprisingly long for a common, low-cost, and chemically modifiable organic semiconductor, the blue pigment copper phthalocyanine (CuPc), see Figure 1, in easily processed thin film form of the type used for device fabrication [1]. Indeed at 5K, reachable using inexpensive closed cycle refrigerators, T1 and T2 are observed to be 59 ms and 2.6 µs, while just above the boiling point of liquid nitrogen at 80 K, they are 10 µs and 1 µs, demonstrating a performance superior to single-molecule magnets over the same temperature range. T2 is over two orders of magnitude greater than the duration of the spin manipulation pulses, which suggests that copper phthalocyanine holds promise for quantum information processing, while the long T1 indicates possibilities for medium-term storage of classical bits in all-organic devices on plastic substrates.

This work was supported by the EPSRC Basic Technologies grant ‘Molecular Spintronics’ (EP/F041349/1 and EP/F04139X/1).

[1] Warner et al. Nature, 2013 (503) 504-508. doi:10.1038/nature12597

Figure 1. Molecular structure of CuPc.

(b) Bilayer Geometry

Mixed Geometry

(a)

(c)

volts

volts

12.10 – 12.30 O18 Christopher Kay Tuesday 8 April

Membrane fusion: A tale of protein conformational exchange, self association and structural heterogeneity

David S. Cafiso, Department of Chemistry and Center for Membrane Biology, University of Virginia, McCormick Road, Charlottesville, Virginia, 22904-4319.

Proteins execute motion over a wide range of amplitudes and time scales, including fast ns librational motions and slower µs conversions between discrete structural substates. A change in distribution of conformational substates is thought to underlie protein allostery and to play a role in protein-protein recognition. We have used a combination of CW and pulse EPR spectroscopy to quantitate protein conformational exchange and structural heterogeneity in membrane proteins and protein complexes. In neuronal exocytosis, the fusion process is tightly regulated and mediated by both protein-protein and protein-membrane interactions. We will describe the use of continuous wave and pulse EPR spectroscopy to characterize conformational exchange in the proteins that mediate neuronal exocytosis, and we will discuss the role that essential regulatory proteins play in regulating this process.

09.00 – 09.40 K3 David Cafiso Wednesday 9 April

Pulse EPR distance measurements on homo-oligomers – from dimer formation to multi-spin artefacts

B.E. Bode

EaStCHEM, Biomedical Sciences Research Complex, and Centre of Magnetic Resonance, University of St Andrews

While the theory for pulsed electron%electron double resonance (PELDOR or DEER) [1] experiments is well-defined for doubly spin-labelled systems distance information from ‘multi-spin’ systems can be severely flawed by artefacts [2] which increase in significance with the number of spin-labels per oligomer [3,4]. Experiments have been reported on homo-oligomeric membrane proteins consisting of up to eight spin-labelled monomers [5].

In this contribution we will present recent results on monitoring dimer formation in viral and bacterial proteins via PELDOR. Furthermore, we will discuss the quality of distance information derived on multi-spin systems with up to eight spins and the prospects of modified experimental and post-processing schemes for accurate distance extraction.

[1] M. Pannier, S. Veit, A. Godt, G. Jeschke, H. W. Spiess, Dead-time free measurement of dipole-dipole interactions between electron spins, Journal of Magnetic Resonance, 2000 (142) 331-340. [2] G. Jeschke, M. Sajid, M. Schulte, A. Godt, Three-spin correlations in double elecron-electron resonance, Physical Chemistry Chemical Physics, 2009 (11) 6580-6591. [3] T. von Hagens, Y. Polyhach, M. Sajid, A. Godt, G. Jeschke, Suppression of ghost distances in multiple-spin double electron-electron resonance, Physical Chemistry Chemical Physics, 2013 (15) 5854-5866. [4] A. Giannoulis, R. Ward, E. Branigan, J. H. Naismith, B. E. Bode, PELDOR in rotationally symmetric homo-oligomers, Molecular Physics, 2013 (111) 2845-2854. [5] G. Hagelueken, W. J. Ingledew, H. Huang, B. Petrovic-Stojanovska, C. Whitfield, H. ElMkami, O. Schiemann, J. H. Naismith, PELDOR Spectroscopy Distance Fingerprinting of the Octameric Outer-Membrane Protein Wza from Escherichia coli, Angewandte Chemie, International Edition, 2009 (48) 2904-2906.

09.40 – 10.00 O19 Bela Bode Wednesday 9 April

Structural insight into (human skeletal muscle) alpha-actinin protein using SDSL in combination with cw and pulsed EPR

Euripedes A. Ribeiro-Jr1, Katharina F. Pirker2, Anita Salmazo1, Nikos Pinotsis1, Claudia Schreiner1, Andrea Ghisleni3, Mathias Gautel3, Enrica Bordignon4 and Kristina Djinovi&-Carugo1

1Department of Structural and Computational Biology, Max F. Perutz Laboratories, University of Vienna, Vienna, Austria. 2Department of Chemistry, University of Natural Resources and Life Sciences, Vienna, Austria. 3New Hunt's House Guy's Hospital, King's College London, UK. 4Department of Physics, Freie Universität Berlin, Germany.

'-actinin is an anti-parallel dimeric muscle protein of 200 kDa. As major component of the Z-disk, it cross-links actin filaments from adjacent sarcomeres. It consists of an N-terminal actin binding domain (ABD), a central rod domain (R1-R4) and a C-terminal calmodulin-like domain with EF-hands 1-2 and 3-4 (Fig. 1). The crystal structure reveals that in the anti-parallel '-actinin dimer the EF3-4 hand is bound to the segment connecting the ABD domain and the rod R1 (i.e. NECK region), which inhibits the EF-hands 3-4 to bind to titin Z-repeats. Titin on the other hand only binds to '-actinin in the presence of PIP2 which is thought to disrupt the interaction between EF-hands 3-4 and the NECK region (Fig. 1), constituting an important step for myofibrillogenesis in skeletal muscle cells. A structure based mutation on '-actinin NECK region was prepared (NEECK mutant) to disrupt the interaction with EF-hands 3-4 and simulate the open conformation.

This study investigates the ABD and EF-hands 3-4 region of '-actinin by spin labelling of naturally occurring cysteine residues (10 per monomer) and determines distances using site-directed spin labelling (SDSL) in combination with cw (X-band) and pulsed (Q-band) EPR spectroscopy. The interaction of "-actinin with titin and PIP2 was investigated and new insight into the dynamics of the protein is provided.

[1] P. Young, M. Gautel, The interaction of titin and !-actinin is controlled by a phospholipid-regulated intramolecular pseudoligand mechanism, The EMBO Journal, 2000 (19) 6331-63

Figure 1. Proposed scheme of the antiparallel actinin structure in the closed and open position after addition of PIP2 (adapted from Young and Gautel, 2000 [1]).

10.00 – 10.20 O20 Katharina Pirker Wednesday 9 April

Spin-Labeling Studies of Protein Conformational Flexibility

Jackie Esquiaqui, Eugene Milshteyn, Zachary Sorrentino, Zhanglong Zhang, Xi Huang, Lingna Hu and Gail E Fanucci

Both continuous wave and pulsed EPR methods are commonly employed with site-directed spin labeling (SDSL) to characterize motions in biological macromolecules. Here we report our groups latest achievements in utilizing SDSL EPR to investigate kink-turn motifs in RNA riboswitches, conformational dynamics in intrinsically disordered proteins and conformational sampling in HIV-1 protease.

11.00 – 11.30 I3 Gail Fanucci Wednesday 9 April

Mechanosensitive channel of small conductance in lipid bilayers studied by PELDOR at X and W band

R. Ward*, C. Pliotas*, E. Branigan*, G. Hagelueken**, R. Hunter***, H. ElMkami***, G. M. Smith***, J. H. Naismith*, O. Schiemann** * Centre for Biomolecular Sciences, University of St. Andrews, St. Andrews, Scotland ** Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn, Germany *** School of Physics and Astronomy, University of St Andrews, St Andrews, UK.

Mechanosensation is a fundamental function in all living organisms. Bacteria use mechanosensitive proteins to protect against cell lysis due to hypoosmotic stress, whilst higher organisms use them for sensing the environment e.g. touch and hearing. The mechanosensitive channel of small conductance (MscS) has been crystallised (Fig. 1) in two different states, which are believed to be the closed [1] and open [2] conformations. One notable feature of these structures is the void that exists between the outer transmembrane helices 1 and 2 and the inner (pore forming) transmembrane helix 3. The functional relevance of this void has been questioned by results from other techniques, which have proposed alternative models and gating mechanisms. Thus it is extremely important to establish whether the void exists in lipid bilayers or is an aretfact of crystallography.

We have already gained strucutral information on the mechanosensitive channel of small conductance (MscS) in detergent micelles [3], but have now gathered further data on this protein in bicelles and nanodiscs, which are lipid bilayer mimics. We have also measured these samples at high field using the HIPER system developed by the Smith group [4]. We conclude that in our lipid bilayer systems the voids are still present and thus need to be taken into account in any mechanistic explanantion of MscS gating. In addition we highlight the advantages of using the HIPER machine, over the X-band system, i.e. improved sample concentration sensitivity and orientational information.

This work is supported by the BBSRC and EPSRC.

[1] Bass, R., et. al. 2002. Science. 298:1582–1587. [2] Wang, W., et. al. 2008. Science. 321:1179–1183. [3] Pliotas, C., et. al. 2012. Proc. Natl. Acad. Sci. USA. 109:E2675–E82. [4] Cruickshank PA, et. al. 2009. Rev. Sci. Instrum. 80:103102.

Figure 1. Structure of MscS. A) Transmembrane helices 1, 2 and 3 coloured in red, green and blue, respectively. B) Heptameric nature of MscS yields a seven spin system when a single monomer is labeled.

11.30 – 11.50 O21 Richard Ward Wednesday 9 April

Influence of mutations on conformational changes during GTP hydrolysis in an ortholog of the human LRRK2 Parkinson kinase analyzed by DEER

Rudi K1, Gilsbach B2, Kortholt A2, Klare JP1

1Department of Physics, Osnabrück University, Osnabrück, Germany 2 Department of Cell Biochemistry, University of Groningen, Groningen, The Netherlands

Leucine-rich repeat kinase 2 (LRRK2) is a dimeric multi-domain protein containing a kinase domain, a GTPase domain (Ras of complex proteins, Roc) appearing in tandem with the COR (C-terminal of Roc) domain [1], and numerous protein–protein interaction domains. Mutations linked to autosomal dominant forms of Parkinson's disease result in alterations in both its enzymatic properties and interactions [2]. For example, the best characterized mutations to date, G2019S in the kinase domain and R1441C and R1441G in the GTPase (G) domain have been reported to influence kinase as well as GTPase activity. We applied site directed spin labeling and distance measurements by Double electron electron resonance (DEER) spectroscopy to study the influence of mutations in the Roc–COR domain tandem of Chlorobium tepidum (Ct), a prokaryotic homologue of the human LRRK2 Parkinson kinase. Our results reveal strong influence of the mutations on the relative motion of the G domains in the Roc-COR dimer.

This work is supported by a grant from the DFG.

[1] Bosgraaf L, Van Haastert PJ (2003) Roc, a Ras/GTPase domain in complex proteins. Biochim Biophys Acta 1643:5–10. [2] Paisán-Ruíz C, et al. (2004) Cloning of the gene containing mutations that cause PARK8-linked Parkinson’s disease. Neuron 44:595–600.

11.50 – 12.10 O22 Johann Klare Wednesday 9 April

PELDOR spectroscopy identifies new structural features of strepto-coccal M3 protein

K. Ackermann1, R. Hagan2, O. Schiemann2, B.E. Bode1, U. Schwarz-Linek2 Biomedical Sciences Research Complex, Centre of Magnetic Resonance and 1School of Chemistry or 2School of Biology, University of St Andrews, St Andrews, Scotland, UK.

Streptococcus pyogenes is a major human pathogen causing about 500,000 deaths per year. Severe streptococcal immune sequelae such as acute rheumatic fever constitute a global health burden.[1] M proteins, located on the bacterial surface, are a key determi-nant of streptococcal virulence. Very little is known about M protein structure and func-tional mechanisms, as the proteins are difficult targets for conventional structural biolo-gy and biochemical approaches. M proteins are generally believed to form elongated, parallel coiled-coil dimers.[2] The N-terminal hypervariable regions (HVR) are of par-ticular interest as they harbour several binding sites for host proteins including colla-gen.[2,3]

In this study, we have used PELDOR spectroscopy to obtain information on the in-solution conformation of the HVR of the M3 protein. The native M3 protein does not contain cysteines, making it an ideal target for EPR using spin-labelled cysteine-containing mutants. A number of these mutants have been produced, with spin labels introduced in regions predicted to adopt or to lack coiled coil topology. This is the first study to provide structural constraints for streptococcal M3 protein. We were able to obtain specific intra-molecular distance information by an unconventional experimental approach, using PELDOR spectroscopy for a protein with unknown struc-ture and no structural homologue available for modelling. We demonstrate the presence of distinct structural features and sharp distance distributions, in particular an unex-pected back-folded conformation of the HVR.

This work was supported by the JABBS Foundation, the Wellcome Trust Institutional Strategic Support Fund (ISSF) and the People Programme (Marie Curie Actions) of the European Union's Seventh Framework Programme (REA 334496).

[1] J.R. Carapetis, A.C. Steer, E.K. Mulholland, M. Weber, The global burden of group A streptococcal diseases, The Lancet Infectious Diseases, 2005 (5) 685-694. [2] P.R. Smeesters, D.J. McMillan, K.S. Sriprakash, The streptococcal M protein: a highly versatile molecule, Trends in Microbiology, 2010 (18) 275-282. [3] K. Dinkla, D.P. Nitsche-Schmitz, V. Barroso, S. Reissmann, H.M. Johansson, I.-M. Frick, M. Rohde, G.S. Chhatwal, Identification of a streptococcal octapeptide motif involved in acute rheumatic fever, The Journal of Biological Chemistry, 2007 (26) 18686-18693.

12.10 – 12.30 O23 Katerin Ackerman Wednesday 9 April

Assembling the H- Cluster of [FeFe] Hydrogenase

R. David Britt Department of Chemistry, University of California, Davis CA 95616

The radical S-adenosylmethionine (SAM) enzyme HydG lyses free L-tyrosine to produce CO and CN- for the assembly of the catalytic H-cluster of [FeFe] hydrogenase. We use electron paramagnetic resonance (EPR) spectroscopy to detect and characterize HydG reaction intermediates generated with a set of 2H, 13C, and 15N nuclear spin labeled tyrosine substrates. We propose a detailed reaction mechanism in which the radical SAM reaction, initiated at an N-terminal [4Fe-4S] cluster, generates a tyrosine radical bound to a C-terminal [4Fe-4S] cluster. Heterolytic cleavage of this tyrosine radical at the Calpha-Cbeta bond forms a transient 4-oxidobenzyl (4OB.) radical and a dehydroglycine bound to the C-terminal [4Fe-4S] cluster. Electron and proton transfer to this 4OB. radical forms p-cresol with the conversion of this dehydroglycine ligand to Fe-bound CO and CN-, a key intermediate in the assembly of the [2Fe] subunit of the H-cluster (1). We apply stopped-flow Fourier transform infrared (SF-FTIR) and electron-nuclear double resonance (ENDOR) spectroscopies to explore in detail the formation of HydG-bound Fe-containing species bearing CO and CN- ligands, with spectroscopic signatures that evolve on the 1 to 1000 s timescale. Through study of the 13C, 15N, and 57Fe isotopologues of these intermediates and products, we identify the final HydG-bound species as an organometallic Fe(CO)2CN synthon that is ultimately transferred to apo-hydrogenase to form the [2Fe]H component of the H-cluster (2). Many open issues remained to be explored in this unique facet of biological cluster synthesis (3), as well as with related radical SAM enzymes.

1. Jon M. Kuchenreuther, William K. Myers, Troy A. Stich, Simon J. George , Yaser NejatyJahromy, James R. Swartz, and R. David Britt. “A Radical Intermediate in Tyrosine Scission to the CO and CN- Ligands of [FeFe] Hydrogenase” Science (2013) 342:472-475

2. Jon M. Kuchenreuther, William K. Myers, Daniel L. M. Suess, Troy A. Stich, Vladimir Pelmenschikov, Stacey A. Shiigi, Stephen P. Cramer, James R. Swartz, R. David Britt, and Simon J. George. “The HydG Enzyme Generates an Fe(CO)2(CN) Synthon in Assembly of the FeFe Hydrogenase H-Cluster” Science (2014) 343:424-427

3. Christopher J. Pickett. “Making the H-Cluster from Scratch” Science (2014) 343:378-379

14.00 – 14.40 K4 David Britt Wednesday 9 April

Continuous-wave EPR at 275 GHz: the case of pseudoazurin

Peter Gast, Freek G.J. Broeren, Silvia Sottini, Takamitsu Kohzuma, Edgar J.J. Groenen Leiden University, Department of Physics, Huygens-Kamerlingh Onnes Laboratory, P.O. Box 9504, 2300 RA Leiden, The Netherlands

Our 275 GHz electron-paramagnetic-resonance spectrometer has been equipped with a new probe head, which contains a single-mode cavity and is especially designed for operation in continuous-wave mode. The enhanced sensitivity and in particular the signal stability that we have achieved with this probe head allows the study of high-spin transition metal sites in proteins. Examples will illustrate that this even applies to Fe(III) sites for which the EPR spectrum at this high microwave frequency can extend over 10 Tesla.

Subsequently the superior resolution at 275 GHz will be demonstrated for pseudoazurin. This protein contains a type 1 copper site with the characteristic coordination by two histidine nitrogens, one cysteine sulfur and one, more weakly bound, methionine sulfur. It turns out that variations in the residues beyond the first coordination sphere have a profound influence on the electronic and geometric structure of the copper site, to such an extent that even multiple conformations show up. We will show that EPR spectra at 275 GHz fully resolve the contributions of a nearly axial spectrum and a rhombic spectrum for pseudoazurins from Achromobacter cycloclastes and from Alcaligenes faecalis. These results will be discussed in relation to optical absorption spectra and X-ray diffraction studies. A similar observation for plastocyanin from Dryopteris crassirhizoma suggests that dual conformations of type 1 copper sites may well be more common.

14.40 – 15.00 O24 Edgar Groenen Wednesday 9 April

Monitoring large domain movements in CoFeSP of Carboxydothermus hydrogenoformans during activation

Ch. Teutloff1, S. Goetzl2, H. Dobbek2, R. Bittl1 1Department of Physics, Freie Universität Berlin, Berlin, Germany 2Institute of Biology, Humboldt-Universität zu Berlin, Berlin, Germany.

The corrinoid iron-sulfur protein (CoFeSP) in Carboxydothermus hydrogenoformans facilitates the methyl group transfer for biosynthesis of acetyl-Coenzyme A. The tightly bound cobalamin cofactor hereby acts as methyl group shuttle by cycling between CH3-Co(III) and Co(I) which is susceptible to oxidation, generating the inactive Co(II) state. Reactivation happens upon interaction and complex formation with the reductive activ-ator of CoFeSP (RACo) [1]. Facilitated by the inherent flexibility of the cobalamin and FeS-cluster binding domain of CoFeSP, the CoFeSP:RACo complex formation leads to large structural changes [2,3]. A mechanistic understanding of CoFeSP from crystal structures is limited due to their static nature. Moreover, since the function of CoFeSP is tightly coupled to the domain movements, insights into the kinetics of these conforma-tional changes will reveal more information about the mechanism of reductive activa-tion and methyl group transfer. To follow domain movements in solution site-directed mutations and labelling with an appropriate marker for subsequent monitoring of structural changes is a qualified bio-physical approach. Here we report about a combined PELDOR and FRET study to in-vestigate the kinetics of domain movements as well as the distance changes involved. E397 of the B12-binding domain at the large subunit of CoFeSP, and E138 at the rigid small subunit were replaced by cysteine followed by labelling with fluorescent (Atto 488, Atto 590) or spin (MTSL) labels for FRET and PELDOR spectroscopy. Our results show a distance reduction by 11 Å upon complex formation, agreeing well with the crystal structure. Furthermore, the transient kinetics show that complex formation is not rate-limiting for reductive activation by RACo.

This work is supported by Cluster of Excellence “Unifying Concepts in Catalysis”.

[1] S. E. Hennig, J. H. Jeoung, S. Goetzl, H. Dobbek, Redox-dependent complex form-ation by an ATP-dependent activator of the corrinoid/iron-sulfur protein, Proc. Natl. Acad. Sci. U.S.A. 2012 (109), 5235–5240. [2] S.E. Hennig, S. Goetzl, J.-H. Jeoung, M. Bommer, F. Lendzian, P. Hildebrandt, H. Dobbek – submitted. . [3] Meister, W., Hennig, S. E., Jeoung, J. H., Lendzian, F., Dobbek, H., and Hildebrandt, P., Complex formation with the activator RACo affects the corrinoid structure of CoFeSP, Biochemistry 2012 (51), 7040–7042.

15.00 – 15.20 O25 Christian Teutloff Wednesday 9 April

Neuroglobins – a playground for EPR spectroscopy

S. Van Doorslaer1 1Department of Physics, University of Antwerp, Antwerp, Belgium.

Neuroglobin, a globin characterized by a bis-histidine ligation of the heme iron, has been identified in mammalian and non-mammalian vertebrates [1,2]. In human neuroglobin, the presence of an internal disulfide bond in the CD-loop is found to modulate the ligand binding through a change in the heme-pocket structure as can be determined by EPR [1]. Although most neuroglobin sequences display conserved Cys, a number of exceptions are known, amongst which the neuroglobins of rodentia, certain amphibia and fishes. In the first part of the talk, the effect of the altered Cys positions on the heme-pocket region will be discussed [2]. Using EPR, it will be shown that the heme-pocket structure is not only modulated by the position of the Cys residues, but also by the surrounding matrix.

The presence of the natural Cys makes human neuroglobin an ideal test system to demonstrate the feasibility of using double electron-electron resonance (DEER) to determine the inter-spin distance between a nitroxide label and a low-spin (S=1/2) heme centre [3]. Three variants of neuroglobin were spin-labelled, each with a spin label on one of the natural Cys positions. The G19-R1 and D5-R1 variants had the least mobile spin labels (Figure 1) and therefore offer the most appropriate systems to determine inter-spin distances. The second part of the talk will focus on the different issues that arise in the distance determinations.

[1] E. Vinck, S. Van Doorslaer, S. Dewilde, L. Moens, Structural change of the heme pocket due to disulfide formation is significantly larger for neuroglobin than for cytoglobin, J. Am. Chem. Soc., 2004 (126) 4516-4517.

[2] W. Van Leuven, B. Cuypers, F. Desmet, D. Giordano, C. Verde, L. Moens, S. Van Doorslaer, S. Dewilde, Is the heme pocket region modulated by disulfide-bridge formation in fish and amphibian neuroglobins as in humans?, Biochim. Biophys. Acta, 2013 (1834) 1757-1763.

[3] M. Ezhevskaya, E. Bordignon, Y. Polyhach, L. Moens, S. Dewilde, G. Jeschke, S. Van Doorslaer, Distance determination between low-spin ferric haem and nitroxide spin label using DEER: the neuroglobin case, Mol. Phys., 2013 (111) 2855-2864.

Figure 1. Graphical representation of spin-label rotamers in human neuroglobin at the natural Cys positions.

16.00 – 16.30 I4 Sabine Van Doorslaer Wednesday 9 April

The O2-tolerant hydrogenase from E. coli and some insights into the unique [4Fe-3S] cluster M. M. Roessler1,2, R. M. Evans2, R. A. Davies2, J. Harmer2,3 and F. A. Armstrong2 1 Queen Mary University of London, School of Biological and Chemical Sciences, Mile End Road, London E1 4NS, UK 2 Department of Chemistry and Centre for Advanced Electron Spin Resonance (CAESR), Oxford University, South Parks Road, OX1 3QR, UK 3Centre for Advanced Imaging, Building 57, The University of Queensland, Brisbane, QLD, 4072, Australia The unusual [4Fe%3S] cluster proximal to the active site plays a crucial role in allowing a class of [NiFe]-hydrogenases to function in the presence of O2 through its unique ability to undergo two rapid, consecutive one-electron transfers [1]. Concurrent with the crystal structure of Escherichia coli Hydrogenase-1, EPR data at X- and W-band for the ‘superoxidised’ P242C variant, in which the medial cluster is ‘magnetically silenced’, reveal two conformations of the proximal [4Fe%3S]5+ cluster (Figure 1), with very different exchange couplings to the active [2]. Furhermore 14N X-band HYSCORE spectroscopy shows two 14N hyperfine couplings attributed to one conformer. The largest, A(14N) = [11.5,11.5,16.0] ± 1.5 MHz, characterises the unusual bond between one Fe (Fe4) and the backbone amide-N of cysteine-20 (see also ref. [3]). The second, A(14N) = [2.8,4.6,3.5] ± 0.3 MHz, is assigned to NC19. The 14N hyperfine couplings are conclusive evidence that Fe4 is a valence-localised Fe3+ in the superoxidised state, whose formation permits an additional electron to be transferred rapidly back to the active site during O2 attack. This work is supported by the EPSRC (supporting CAESR) and by the BBSRC (to F. Armstrong). [1] M. E. Pandelia et al., PNAS, 2011, 108, 6067. [2] M. M. Roessler et al., JACS, 2012, 134, 15581. [3] C. Teutloff et al., in The 45th Annual International Meeting of the EPR Spectros-copy Group of the Royal Society of Chemistry, University of Manchester, 2012

Figure 1. The proximal [4Fe-3S]5+ cluster in E. coli Hyd-1, illustrating the oscillation of Fe4 in the two conformations of the cluster.

16.30 – 16.50 O26 Maxie Roessler Wednesday 9 April

Advanced electron paramagnetic resonance on the catalytic iron sulphur cluster bound to the CCG domain of heterodisulfide reductase

and succinate: quinone reductase

A. J. Fielding,1,5 K. Parey,2,3 U. Ermler,3 S. Scheller,4 B. Jaun,4 and M. Bennati5

1 Photon Science Institute, The University of Manchester, UK. 2 Max-Planck Institute for Terrestrial Microbiology, Marburg, Germany. 3 Max-Planck Institute for Biophysics, Frankfurt, Germany. 4 Department of Chemistry, ETH-Zurich, Switzerland. 5 Max-Planck Institute for Biophysical Chemistry, Göttingen, Germany.

Heterodisulfide reductase (Hdr) is a key enzyme in the energy metabolism of methanogenic archaea [1]. The enzyme catalyses the reversible reduction of the heterodisulfide (CoM-S-S-CoB) to the thiol coenzymes, coenzyme M (CoM-SH) and coenzyme B (CoB-SH). Cleavage of CoM-S-S-CoB at an unusual FeS cluster reveals unique substrate chemistry. The cluster is fixed by cysteine’s of two cysteine-rich CCG domain sequence motifs (CX31-39CCX35-36CXXC) of subunit HdrB of the Methanothermobacter marburgensis HdrABC complex [2]. We report on 34 GHz 57Fe Electron- Nuclear Double Resonance (ENDOR) spectroscopic measurements on the oxidized form of the cluster found in HdrABC and in two other CCG domain containing proteins, recombinant HdrB of Hdr from M. marburgensis and recombinant SdhE of succinate: quinone reductase from Solfolobus solfataricus P2. The spectra at 34 GHz show clearly improved resolution arising from the absence of proton resonances and polarization effects. Systematic spectral simulations of 34 GHz data combined with previous 9 GHz data [3] allowed the unambiguous assignment of four 57Fe hyperfine couplings to the cluster in all three proteins. 13C Mims ENDOR spectra of labelled CoM-SH were consistent with the attachment of the substrate to the cluster in HdrABC, whereas in the other two proteins no substrate is present.57Fe resonances in all three systems revealed unusually large 57Fe ENDOR hyperfine splitting as compared to known systems. The results infer that the cluster unique magnetic properties arise from the CCG binding motif.

[1] R.K. Thauer, A.K. Kaster, H. Seedorf, W. Buckel, R. Hedderich, Nat Rev Microbiol, 2008 (6) 579-591. [2] R. Hedderich, J. Koch, D. Linder, R.K. Thauer, Eur J Biochem 1994 (225) 253-261. [3] M. Bennati, N. Weiden, K.P. Dinse, R. Hedderich, J Am Chem Soc 2004 (126) 8378-8379.

16.50 – 17.10 O27 Alistair Fielding Wednesday 9 April

Haptoglobin binding to haemoglobin changes the micro-environment of aTyr42, effecting in a lower reactivity of its radical state generated by H2O2 :

a stopped-flow EPR study

Dimitri A. Svistunenko1, Andreea Manole1,2

1School of Biological Sciences, University of Essex, Colchester, Essex CO4 3SQ, UK 2Current address: UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK

In a number of pathological conditions, haemoglobin (Hb) escapes the safe environment of the red blood cells, undergoes oxidation to an inactive, in terms of O2-binding, ferric (Fe3+) state and becomes toxic. The toxicity is caused by the high reactivity of the ferric Hb (metHb) with hydrogen peroxide (H2O2). The short-lived intermediate of the reaction, the globin-bound radical is able to inflict oxidative damage to many cell components. Haptoglobin (Hp) is a plasma protein (not containing a haem group in spite of similarity in names) which irreversibly binds Hb for further safe removal from organism. Interestingly, Hb in the Hp-Hb complex is much less reactive with H2O2 effecting in significantly less damage to other molecules. To study the mechanism of such diminished oxidative reactivity, we used rapid (5 s per CW scan) detection of the radical formed immediately under peroxide addition to human Hb or Hp-Hb complex.

We found that fast scanning of EPR spectra results in an error in the magnetic field values recorded for a spectrum. Correction of these errors by using a Bruker Teslameter was important for finding accurate spectral parameters, such as principal g-values and hyperfine interaction constants.

The latter parameters determined by spectra simulation for the radical in Hb and in Hp-Hb complex were used: 1) to identify the Tyr residue most likely to be the site of observed radical as Tyr42, 2) to conclude that this residue in the complex is characterised by notably more hydrophobic micro-environment than in unbound Hb.

Considering the crystal structure of a Hp-Hb complex (for porcine proteins) [1], we conclude that vast surface area of interaction of the two proteins, spread over two Hb subunits, serves to insulate the

Figure 1. Consecutively measured spectra of metHb reacting with H2O2.

potentially reactive site from the surroundings. Such a mechanism ensures that the highly reactive state of Hb, created by H2O2, lives longer ultimately producing less damage.

[1] Andersen, C. B.; Torvund-Jensen, M.; Nielsen, M. J.; de Oliveira, C. L.; Hersleth, H. P.; Andersen, N. H.; Pedersen, J. S.; Andersen, G. R., and Moestrup, S. K. (2012) Structure of the haptoglobin-haemoglobin complex. Nature, 489, 456-459.

17.10 – 17.30 O28 Dimitri Svistunenko Wednesday 9 April

PsaBCA and manganese acquisition: Elucidating the molecular basis of metal ion selectivity and binding by Gram positive bacteria

Alex Morley1, Jessica H. van Wonderen1, Stephanie L. Begg2, Rebecca Campbell2, Bostjan Kobe3, James C. Paton2, Megan L. O'Mara3, Christopher A. McDevitt2 and Fraser MacMillan1 1Henry Wellcome Laboratory for Biological EPR, School of Chemistry, Norwich, NR4 7TJ, UK 2Research Centre for Infectious Diseases, School of Molecular and Biomedical Science, University of Adelaide, South Australia, 5005, Australia. 3School of Chemistry and Molecular Biosciences, University of Queensland, Brisbane, Australia Streptococcus pneumoniae is one of the world’s foremost bacterial pathogens. Annually infections associated with S. pneumoniae cost the world’s economy > several $billion and globally it is responsible for > 1 million deaths. S. pneumoniae infections are dependent on the acquisition of metals from the host environment. Manganese (Mn) is essential for pneumococcal virulence and is specifically acquired by the pneumococcal surface antigen protein A (PsaA), which is the substrate-binding protein component of an ATP-binding cassette (ABC) transport pathway (PsaBC). Although the role of PsaA in Mn acquisition has been definitively established in both in vitro and in vivo studies, the mechanism of metal binding remains poorly understood. Here we present new data on the molecular determinants of metal binding by PsaA and the potential implications for host-pathogen interaction. This Mn2+ substrate-binding protein, PsaA also reveals a strong Zn2+ binding even though it is not transported. Metal competition is postulated to play a role in immune defence. We propose to design and create site-directed variants that will allow us to develop a site-directed spin-labelling (SDSL) approach to look at dynamic structural differences upon Mn2+ and Zn2+ binding in comparison to various crystal structures. The ultimate aim is to distinguish between two distinct metal binding mechanisms using a combination of biochemistry together with PELDOR spectroscopy and computational simulations. In addition, this work also directly reveals how the biological functions of proteins are ultimately beholden to the fundamental laws of chemistry.

09.20 – 09.40 O29 Fraser MacMillan Thursday 10 April

Probing nematic and discotic liquid crystals by a combination of EPR spectroscopy and theoretical modeling

F. Chami,1 H. Gopee,1 A.N. Cammidge,1 M.R. Wilson,2 and V.S. Oganesyan1 1 School of Chemistry, University of East Anglia, Norwich, NR4 7TJ, United Kingdom 2 Department of Chemistry, Durham University, Durham, DH1 3 LE, United Kingdom

In this presentation we report our recent application of variable temperature EPR spectroscopy with different nitroxide spin probes (SPs) combined with theoretical modeling to both nematic and discotic (columnar) liquid crystals (LCs). Such a combined approach bridges the gap between theory and experiment allowing unambiguous interpretation of EPR lineshapes and enabling conclusions to be drawn about molecular motions and order in the bulk phase [1,2]. For nematic LCs structurally variable nitroxide SPs probing different aspects of LC dynamics have been employed resulting in different but highly complementary EPR spectra. Variable temperature EPR spectra of LCs doped with SPs are predicted directly from fully atomistic Molecular Dynamics (MD) simulations using our recently developed MD-EPR simulation methodology [1]. They show excellent agreement with experiment. Using MD-EPR approach we were able to characterise in detail the dynamics and molecular interactions in different phases of nematic LCs including meta-stable states at the phase transitions [3]. We also present the first application of EPR spectroscopy to columnar discotic liquid crystal (HAT6) using a novel rigid-core nitroxide spin probe designed and synthesized by us for this purpose (see picture below) [4]. EPR spectra measured at different temperatures across three phases show a strong sensitivity to the HAT6 phase composition, molecular rotational dynamics, and columnar order as well as the director distribution. Simulation of the EPR line shapes using a Brownian Dynamics (BD) simulation model gives a numerical estimate of these parameters at different temperatures along both I-Col and Col-Cr phase transitions.

[1] V.S. Oganesyan, Phys. Chem. Chem. Phys., 2011, 13, 10, 4724. [2] V.S. Oganesyan, E. Kuprusevicius, H. Gopee, A.N. Cammidge, M.R. Wilson, Phys. Rev. Lett., 2009, 102, 013005. [3] F. Chami, M.R. Wilson and V.S. Oganesyan, Soft Matter, 2012, 8, 6823. [4] H. Gopee, A.N. Cammidge and V.S. Oganesyan, Angew. Chem. Int. Ed., 2013, 52, 34, 8917.

09.40 – 10.00 O30 Vasily Oganesyan Thursday 10 April

Pseudocontact shift from distributed paramagnetic centres G.T.P. Charnock1, Ilya Kuprov2 1Computer Science Department, University of Oxford, Oxford, UK. 2School of Chemistry, University of Southampton, Southampton, UK.

An estimated one third of all proteins are metalloproteins, of which a signicant number are paramagnetic. In the context of magnetic resonance spectroscopy the presence of unpaired electrons is advantageous because it enables extraction of structural information, in particular from pseudocontact shift – effective additional shielding of the nuclei via dipolar interaction with the unpaired electrons. Typically, the unpaired electron is approximated as a point dipole sitting at a single point in space [1]. The aim of the work presented here is to attempt to model the electron spin density distribution generating the pseudocontact shift more realistically as a distributed dipole. Another objective is to derive a partial differential equation that PCS should conform to as a scalar field – from the analogy with Poisson's equation it is clear that some kind of elliptic second-order PDE should be obeyed, but the exact form of low-order and source terms is not currently known. This work is supported by EPSRC (EP/F065205/1, EP/H003789/1). We are also grateful to Gottfried Otting for drawing our attention to the problem.

[1] I. Bertini, C. Luchinat, G. Parigi, R. Pierattelli, ChemBioChem 6 (2005) 1536. [2] M.A. Keniry et al., J. Bacteriol. 188 (2006) 4464.

Figure 1. Difference between the point and the delocalized model of pseudocontact shift (isovalues in ppm) in Dy3+ substituted theta and epsilon sub-units [2] of E. Coli DNA polymerase III. Figure 2. Improvement in residual point scatter between the point electron and the delocalized electron model of pseudocontact shift in Dy3+ substituted theta and epsilon sub-units [2] of E. Coli

10.00 – 10.20 O31 Ilya KuprovThursday 10 April

Hydrogen in diamond: Defects and Diffusion

M.E. Newton1, C. B. Hartland1, P. M. Martineau2, D. Fisher2, D. J. Twitchen3, and B. L. Green3 1Department of Physics, University of Warwick, UK 2De Beers Technologies (UK) Ltd., Maidenhead, UK 3Element Six Ltd., Harwell, UK

Recent experimental work has raised many questions about the incorporation and diffusion/migration of hydrogen in diamond, as well as the role it plays in influencing defect reactions and the bulk properties of diamond. Recently, a new family of hydrogen related defects NV:H, N2V:H and N3V:H has been identified in as-grown, annealed or multiply processed diamond grown by chemical vapour deposition. These defects incorporate a lattice vacancy (V) where one or more of the four neighbouring carbon atoms have been replaced by a nitrogen (N) impurity; a hydrogen (H) is trapped in the vacancy. Furthermore, the aggregation of nitrogen in diamond grown by chemical vapour deposition does not appear to follow the pattern established in the study of High Pressure High Temperature (HPHT) synthetic and natural diamond. It has been suggested that a high concentration of hydrogen incorporated into the diamond, relative to that of nitrogen, alters the reaction pathways. Also a reduction in the optical emission from nitrogen vacancy (NV) centres in single crystal diamond that has been exposed to hydrogen plasmas, was attributed to the formation of NV:H centres by the plasma-induced in-diffusion of hydrogen to NV centres.

Laboratory and natural synthesis of diamond will be reviewed, and the role that hydrogen plays will be discussed. New multi-frequency EPR data will be presented on the NnV:H defects, and the unusual features of these paramagnetic centres described. In light of this data, our understanding of the migration and trapping of hydrogen in diamond will be reviewed with reference to what this tells us about processes that occur over geological time scales at HPHT deep within the Earth and how we might develop diamond based Quantum Technologies. The authors gratefully acknowledge the support of De Beers Technologies UK Ltd., EPSRC and the chist-era project Quantum Information with NV Centres (QINVC).

11.00 – 11.30 I5 Mark Newton Thursday 10 April

Charge Separation in Organic Solar Cells probed by Transient EPR J. Behrends1, F. Kraffert1, R. Bittl1 1Fachbereich Physik, Freie Universität Berlin, Berlin, Germany.

Using transient electron paramagnetic resonance (trEPR) spectroscopy we analyse the process of free charge carrier generation in organic solar cells. Prior to dissociation of photogenerated excitons into separated charges, bound polaron pairs (also referred to as charge transfer states) form at the donor/ acceptor interface. There is consensus that charge transfer states may critically influence the yield of free charge carriers, but their exact role is being controversially discussed at the moment [1,2]. Here we report trEPR measurements with submicrosecond time resolution performed on polymer: fullerene blends. We show that the trEPR spectrum immediately following photoexcitation reveals signatures of spin-correlated polaron pairs and thus decisively differs from the spectrum of separated polarons commonly observed in light-induced cwEPR. The pair partners (positive polarons on the donor and negative polarons on the acceptor) can be identified by their characteristic g values. The fact that the population of the polaron pair states strongly deviates from Boltzmann equilibrium unambiguously shows that both constituents of each pair are geminate, i.e., originate from the same exciton [3]. We discuss the role of coupled charge carrier pairs in mediating the conversion from excitons into separated charges as probed by trEPR. Particular emphasis will be given to triplet excitons, which are encountered in some donor:acceptor systems used in high-efficiency organic solar cells.

[1] A.A. Bakulin, A. Rao, V.G. Pavelyev, P.H.M. van Loosdrecht, M.S. Pshenichnikov, D. Niedzialek, J. Cornil, D. Beljonne and R.H. Friend, The Role of Driving Energy and Delocalized States for Charge Separation in Organic Semiconductors, Science, 2012 (335) 1340. [2] K. Vandewal et al., Efficient charge generation by relaxed charge-transfer states at organic interfaces, Nature Mater., 2014 (13) 63. [3] J. Behrends, A. Sperlich, A. Schnegg, T. Biskup, C. Teutloff, K. Lips, V. Dyakonov and R. Bittl, Direct detection of photoinduced charge transfer

11.30 – 11.50 O32 Jan Behrends Thursday 10 April

Spin-locking in low-frequency RYDMR

C. J. Wedge,1 Jason C. S. Lau,2 Kelly-Anne Ferguson,3 Stuart A. Norman,3 P. J. Hore2 and Christiane R. Timmel3

1Department of Physics, University of Warwick, Coventry. 2Physical & Theoretical Chemistry Laboratory, Department of Chemistry, University of Oxford. 3Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford. The purported effects of weak magnetic fields on various biological systems from animal magnetoreception to human health have generated widespread interest and sparked much controversy in the past decade. To date the only well established mechanism by which the rates and yields of chemical reactions are known to be influenced by weak magnetic fields is based on the spin-dependent reactivity of radical pairs. Reaction yield detected magnetic resonance (RYDMR), has been proposed as a diagnostic test for the operation of the ‘radical pair mechanism’ [1]. Whereas the effect of a weak static magnetic field alone could be argued to arise from other mechanisms, in combination with a radiofrequency oscillating field a resonance response is indicative of the radical pair mechanism. Application of this technique in animal behavioural experiments has provided strong evidence in support of avian magnetoreception operating through a magnetically sensitive chemical reaction, rather than the opposing hypothesis of a compass needle response of magnetite particles [2]. The effects on radical pair reactions of applying relatively strong radiofrequency oscillating fields, both parallel and perpendicular to the static field, will be reported. We highlight the importance of understanding the effect of the strength of the radiofrequency oscillating field, demonstrating that there is an optimal oscillating field strength above which the observed signal decreases in intensity and eventually inverts (Fig 1). We establish the correlation between the onset of this effect and the hyperfine structure of the radicals involved, identify the existence of ‘overtone’ type features appearing at multiples of the expected resonance field position, and explore the use of these effects in measuring electron self-exchange kinetics and radical pair lifetimes [3].

[1] K. Henbest et al., Radio Frequency Magnetic Field Effects on a Radical Recombination Reaction: A Diagnostic Test for the Radical Pair Mechanism, J. Am. Chem. Soc., 2004 (126) 8102–8103.

[2] T. Ritz et al., Resonance effects indicate a radical-pair mechanism for avian magnetic compass, Nature, 2003 (429) 177–180.

[3] C.J. Wedge et al., Spin-locking in low-frequency reaction yield detected magnetic resonance, Phys. Chem. Chem. Phys., 2013 (15) 16043–16053

11.50 – 12.10 O33 Chris Wedge Thursday 10 April

Fig 1. Schematic representation of the different types of RYDMR experiment.

EPR studies of the conformations and dynamics of the protein kinase activation loop.

Maria Grazia Concilio1, Alistair J Fielding1, Selena Burgess2, Richard Bayliss2 1Photon Science Institute, University of Manchester, United Kingdom. 2Department of Biochemistry, Henry Wellcome Building, University of Leicester, United Kingdom.

Aurora-A is a miotic Ser/Thr protein kinase that controls many cellular path-ways and its activity is tightly regulated by changes in conformation. Kinase function is implicated in a wide range of diseases including cancer1-2 and a conserved region known as the activation loop is crucial for the activity of many kinases.2 Therefore, studies of kinase activation through characterisation of their conformation, is important to enhance understanding of molecular processes related to diseases and to support the discovery of small molecule kinase inhibitors.

To characterize and resolve conformations and dynamics of the protein kinase, a series of CW EPR and double electron-electron resonance (DEER) measurements, supported by spectral simulations, were carried out to determine average distances and distance distributions from spin-label pairs introduced via site-directed mutagenesis at positions T288 (activation loop, purple region) and E170 (helix, blue region) in Aurora-A kinase (Figure 1). Broad distance distributions and multiple populations were identified, indicating flexibility of the structure. Variation of the distance distribution was observed upon addition of four different protein kinase inhibitors. These changes were attributed to differences in conformational space accessible to the activation loop. High field (95 GHz) experiments also showed a change in polarity of the environment of the spin label at position T288 on addition of ligands and protein binding partners.

[1] Lahiry, P.; Torkamani, A.; Schork, N. J.; Hegele, R. A. Kinase mutations in human disease: interpreting genotype-phenotype relationships. Nat Rev Genet. 2010, 11, 60. [2] Rowan, F. C.; Richards, M.; Bibby, R. A.; Thompson, A.; Bayliss, R.; Blagg, J. In-sights into Aurora-A kinase activation using unnatural amino acids incorporated by chemical modification. ACS Chem. Biol. 2013, 8, 2184.

Figure 1: Illustration of the two selected sites 170 (helix, blue region) and 288 (activation loop, pur-ple region) of Aurora-A kinase protein (from resi-due 122 to residue 403). Data based on the X-ray crystallography model with Protein Data Bank (PDB) identifier, 1OL7.2

P1 Maria Concilio “EPR studies of the conforma5ons and dynamics of the protein kinase ac5va5on loop”

HIGH PRESSURE CHEMISTRY: ELECTRON TRANSFER IN IONIC LIQUIDS MEASURED BY ELECTRON SPIN RESONANCE SPECTROSCOPY. B. Sudy1, K. Rasmussen1, G. Grampp1. 1Institute of Physical and Theoretical Chemistry,Graz University of Technology, Austria It is well-known that the kinetics of organic electron self-exchange reactions may be studied by ESR linebroadening experiments [1, 2].

! " " ! The solvent dependence of the rate constants obtained are normally described using the Marcus Theory and mainly depend on the outer reorganisation energy o, wich is a func-tion of the solvent refractive index nD s o = f (nD, ). Classically, both static and dynamic solvent effects have been studied by choosing sol-vents with appropriate variations in physical properties [2, 3]. Here we report the et-rate con-stants obtained in different ionic liquids. We have built a high-pressure system enabling us to apply pressures of up to 100 MPa to solutions and since several key solvent properties (viscos-ity, dielectric constant, relaxation times, refrac-tive index) are pressure dependent, we are now able to emulate ‘solvent effects’ through pres-sure variations. This is done by determining the volume of acti-vation of the reaction, which in cases where a neutral reactant is present may be written as the sum of only two contributions, namely outer reorganization (OR) and solvent dynamics (SD).

‡ ‡ ‡ln etOR SD

T

kV RT V VP

Several well-known self-exchange systems [4] have been investigated in some common imidazolium based ionic liquids using ESR spectroscopy at room temperature and at variable temperatures or pressures. The experimental results, such as rate constants, reorganization energies or solvent dynamic effects are compared to their analogues from traditional solvents, as well as to existing findings from literature, obtained using other experimental methods.

!< #+,"-,%./01#$=+>/#72,'')2,#0/,3+'(26?#,:,0(2-1#(241'.,2#+1#+-1+0#:+@)+*'#3,4')2,*#A6#%:,0(2-1#B7+1#&,'-1410,#B7,0(2-'0-76;#

[1] R. L. Ward , S. I. Weissman, Electron Spin Resonance Study of the Electron Exchange between Naphthalene Negative Ion and Naphthalene, Journal of the American Chemical Society, 1957 (79) 2086-2090. [2] N. M. Atherton, M. J. Davies, B. C. Gilbert and G. Grampp, Electron transfer kinetics studied by EPR/ESR and related methods, 1998 (16) 234-267. [3] G. Grampp, K. Rasmussen, Solvent dynamical effects on the electron self- = 2,2,6,6-tetramethyl- 1-piperidinyloxy radical) Part I. ESR-linebroadening measurements at T = 298 K, Phys. Chem. Chem. Phys, 2002 (4) 5546-5549. [4] K. Rasmussen, T. Hussain, S. Landgraf, G. Grampp, High Pressure ESR Stud- ies of Electron Self-Exchange Reactions of Organic Radicals in Solution, J. Phys. Chem. A, 2012 (116) 193-198. [5] T. Hussain, K. Rasmussen, A. I. Kokorin, G. Grampp, High-pressure EPR spectroscopy: paramagnetic exchange of organic radicals with iron (III) acety- lacetonate, Mol. Phys. , 2013 (111) 2717-2722.

Solvent dynamical effects on the electron selfSolvent dynamical effects on the electron selftetramethyltetramethyl

Artificially maturated [FeFe] hydrogenase from C.reinhardtii: HYSCORE and ENDOR study of a non-natural H-cluster

Agnieszka Adamska-Venkatesh1, Trevor Simmons2, Judith Siebel1, Vincent Artero2, Edward Reijerse1, Wolfgang Lubitz1

1Max-Planck-Institut für Chemische Energiekonversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany. 2Laboratoire de Chimie et Biologie des Métaux (CEA / Université Grenoble 1 / CNRS), 17 rue des Martyrs, F-38054 Grenoble cedex 9, France.

Hydrogenases are enzymes which catalyze the oxidation of H2 as well as the reduction of protons to form H2. The active site of [FeFe] hydrogenase is referred to as the “H-cluster” and consists of a “classical” [4Fe4S] cluster connected via a protein cysteine side group to a unique [2Fe]H sub-cluster containing CN- and CO ligands as well as a dithiol bridging ligand. It was shown that various biomimetic complexes of the diiron sub-cluster can be inserted with the help of the maturation protein HydF [1] or even directly [2] into apo-protein of [FeFe] hydrogenase, which contains only the [4Fe-4S] part of the H-cluster. In a more recent study we discovered that oxidized [FeFe] hydrogenase from Chlamydomonas reinhardtii maturated with the non-natural biomimetic complex [Fe2(CO)4(CN)2(pdt)]2- in which the bridging amine is replaced by CH2 strongly resembles the active oxidized (Hox) state of the native protein [3]. The Hox state is EPR active and the signal originates from the mixed valence FeIFeII state of the diiron subcluster [4]. Taking advantage of the readily available isotope labeled biomimetic complex as well as the possibility to obtain a pure redox state we performed HYSCORE and ENDOR studies of the 13C and 15N labeled non-natural H-cluster. Two 13C hyperfine couplings were observed and assigned to CN- ligands bound to terminal and proximal irons. Only one 15N coupling was detected and assigned to the CN- ligand bound to the terminal iron. The natural abundance HYSCORE spectra of this artificially generated protein are compared with those of the native enzyme [4]. [1] G. Berggren, A. Adamska, C. Lambertz, T. Simmons, J. Esselborn, M. Atta, S.

Gambarelli, J. Mouesca, E. Reijerse, W. Lubitz, T. Happe, V. Artero, M. Fontecave, Biomimetic assembly and activation of [FeFe]-hydrogenases, Nature 2013, 499 (7456), 66-69.

[2] J. Esselborn, C. Lambertz, A. Adamska-Venkatesh, T. Simmons, G. Berggren, J. Nothl, J. Siebel, A. Hemschemeier, V. Artero, E. Reijerse, M. Fontecave, W. Lubitz, T. Happe, Spontaneous activation of [FeFe]-hydrogenases by an inorganic [2Fe] active site mimic, Nature Chemical Biology 2013, 9 (10), 607-609.

[3] A. Adamska-Venkatesh, D. Krawietz, J. Siebel, K. Weber, T. Happe, E. Reijerse, W. Lubitz, Artificially maturated [FeFe] hydrogenase reveals new redox states, (in preparation)

[4] A. Silakov, B. Wenk, E. Reijerse, W. Lubitz, (14)N HYSCORE investigation of the H-cluster of [FeFe] hydrogenase: evidence for a nitrogen in the dithiol bridge, Physical Chemistry Chemical Physics 2009, 11 (31), 6592-6599.

P3 Agnieszka Adamska-‐Venkatesh “Ar5ficially maturated [FeFe] hydrogenase from C.reinhard5i: HYSCORE and ENDOR study of a non-‐natural H-‐cluster”

NOx reduction with hydrocarbons on nickel metallozeolite investigated with CW-EPR and HYSCORE spectroscopy and DFT modelling T. Mazur1, K. Podolska-Serafin1, P. Pietrzyk1, M. Chiesa2, Z. Sojka1

1Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Krakow, Poland. 2Department of Chemistry, University of Torino, Via P. Giuria. 7, 10125 Torino, Italy . Most of the reaction steps involved in the Selective Catalytic Reduction (SCR) of NOx over metallozeolites are connected with pronounced charge and spin density redistribution between the active center constituted by transition metal ion and the gas-phase reactants. Useful detailed information on the reaction mechanism can be obtained from analysis of the resulting paramagnetic intermediates by means of EPR-related techniques. Combined with comprehensive DFT calculations (relativistic ZORA-SOMF/B3LYP method) of spectral parameters, and analysis of electron and spin density flow channels, they provide detailed insight into the structure of the intermediates and their nearest chemical environment [1]. Herein we report on spectroscopic characterization of nickel (II/I) centers dispersed within the ZSM-5 zeolite and their adducts with the key reactants of the SCR process. As screened with in situ CW-EPR method, NO is selectively captured by the metal centers from the reaction SCR mixture to form primary nitrosyl intermediates (Ni2+NO). Its reaction with hydrocarbon reductors (C2H4 and C2H2) leads to the formation of CN and NCO surface groups evidenced with operando DRIFT and pulse EPR measurements. Apart from the parent nitrosyls, the CN and NCO adducts contribute to the complicated 14N HYSCORE patterns shown in Figure 1. Further analysis of the spectra involving computer simulations and DFT calculations of 14N hyperfine and quadrupole coupling parameters provided first unambiguous evidence for identity and structure. [1] P. Pietrzyk, T. Mazur, K. Podolska-Serafin, M.

Chiesa, Z. Sojka, Journal of the American Chemical Society, 2013 (135) 15467-15478.

T.M. thanks the International PhD studies program at the Faculty of Chemistry, Jagiellonian University, within the MPD Program of the Foundation for Polish Science co-financed by the EU Regional Development Fund for supporting his stay at the University of Torino.

Figure 1. CW-EPR and HYSCORE spectra for in situ reaction between Ni(II)ZSM-5 nitrosyl adduct and C2H4

P4 Tomas Mazur “NOx reduc5on with hydrocarbons on nickel metallozeolite inves5gated with CW-‐EPR and HYSCORE spectroscopy and DFT modelling”

PELDOR on Trimeric Betaine Symporter BetP B. Endeward1, I. Waclawska2, H. H. Haeri1, C. Ziegler2,3, T. Prisner1

1Institute of Physical and Theoretical Chemistry and Center for Biomolecular Magnetic Resonance (BMRZ), Goethe University, Frankfurt, Germany. 2Department of Structural Biology, Max Planck Institute of Biophysics, Frankfurt, Ger-many. 3Department of Biophysics II, University Regensburg, Regensburg, Germany. PELDOR (pulsed electron electron double resonance [1]) is a magnetic resonance method for distance, orientation, and dynamic measurements of two or more paramagnetic centers in macromolecules like proteins, RNA, or DNA as well as polymers. Here we apply this method to analyze the different states of the trimeric betaine symporter BetP [2-3]. This symporter does activate at osmotic stress and transports betaine and sodium through the membrane. BetP cycles through several states during the transport. From the periplasmic open via an occluded to a cytoplasmic open state. One open question on the trimeric transport is whether it occurs on all three monomers synchronously or in a cyclic sequence. By PELDOR and site-directed spin labeling we probe the changes on activation as well as the occurring different states. We will report on the current status a this ongoing project. This work is financially supported by DFG-CRC 807, BMRZ and Goethe University. [1] A. Milov, K. Salikov, M. Shirov, Fiz. Tverd. Tela., 1981 (23) 975-982. [2] S. Ressl, A.C. Terwisscha van Scheltinga, C. Vonrhein, V. Ott, C. Ziegler, Molecu-

lar basis of transport and regulation in the Na(+)/betaine symporter BetP Nature 2009 (458) 47-52.

[3] L. Forrest, R. Krämer, C. Ziegler, The structural basis of secondary active transport mechanisms. Biochim Biophys Acta 2011 (1807) 167-188.

P5 Burkhard Endeward “PELDOR on Trimeric Betaine Symporter BetP”

Site Directed Spin Labelling of Bio-Macromolecular Complexes: Cysteine Mutagenesis VS Genetic Code Expansion

Stacey Bell1, Paul N. Barlow2, Sarah Thomas2, Alison N. Hulme2, Janet E. Lovett2. 1 School of Physics & Astronomy, BMS Building, University of St Andrews, St Andrews, KY16 9ST, U.K.

2 EaStCHEM School of Chemistry, University of Edinburgh, Edinburgh EH9 3JJ, U.K.

Using DEER to Explore the Complement C3b: Factor H Complex in Solution The Complement system straddles both the innate and adaptive immune systems, providing a potent first line in defence. The system is a cascade of enzymatic cleavages, one of which is the conversion of component C3 to C3b which marks target cells for destruction. Deposition of C3b is indiscriminate and must be tightly regulated. One reg-ulating protein is factor H (fH) which acts both as a cofactor during the cleavage of C3b to inactive iC3b and through decay acceleration of the activating convertFH is a 155kDa glycoprotein comprising of twenty domains and with a total of 40 disul-fide bonds. It carries out its function by having two distinct binding sites for C3b, the four most N terminal domains (fH1-4) and the two domains at the C terminus (fH19-20). However, while the binding sites for the fH:C3b complex have been identified and structures for the fH(1-4):C3b1 and fH(19-20):C3b2 complexes proposed, it is not known whether it is possible that fH could bind at both sites on C3b simultaneously. DEER will be used to determine whether the popular idea of the -plausible as well as to validate the previously proposed structures. Preparation of the truncated fH cysteine mutants and purification of C3b from human plasma as well as EPR results will be described in detail.

A Need for New Spin Labelling Methods?

Traditional methods of site-directed spin-labelling involving cysteine substitution muta-genesis are effective, but what happens when this is not feasible? Where a protein ex-hibits native free cysteines it may be possible to site specifically label incorporated

n 3. We are developing new methods for labelling unnatural ami--

be presented.

fH

Figure 1: Schematic representation of fH bound to C3b. In this model fH1-4 and fH19-20 occupy a single molecule of C3b. The remaining do-mains of fH, which do not bind C3b, exhibit this bent-back structure. The 3 small circles repre-sent spin-labelling sites on both fH and C3b.

[1] Wu, J., Wu, Y.Q., Ricklin, D., Janssen, B.J.C., Lambris, J.D & Gros, P. Structure of C3b-factor H and implications for host protection by complement regula-

tors, Nature Imunol. 10, 728-733 (2009)

[2] Morgan, H.P., Schmidt, C.Q., Guariento, M., Blaum, B.S., Gillespie, D., Herbert, A.P., Kavanagh, D., Mertens, H.D.T., Svergun, D.I., Johansson, C.M., Uhrin,

D., Barlow, P.N., Hannan, J.P. Structural basis for engagement by complement factor H of C3b on a self surface. Nat Struct Mol Biol. 2011; 18, 463-470

[3] Fleissner, M.R., Brustad, E.M., Kalai, T., Altenbach, C., Cascio, D., Peters, F.B., Hideg, K., peuker, S., Schultz, P.G., Hubbell, W.L. Site-directed spin labelling

of a genetically encoded unnatural amino acid. Proc Natl Acad Sci U S A. 2009 Dec. 22;106(51):21637-42

C3b

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A ferroelectric ordered state associated with a synchronised proton-electron transfer in mixed-valence Rhenium (III)-Rhenium (IV) com-plexes as studied by single-crystal ESR spectroscopy and quantum chemical calculations Takeshi Yamane1, Kazunobu Sato1,3, Shunsuke Tatsumi1, Kenji Sugisaki1,3, Yuki Kanzaki1,3, Kazuo Toyota1,3, Daisuke Shiomi1,3 Makoto Yoshizawa2, Makoto Tadokoro2and Takeji Takui1,3 1Graduate School of Science, Osaka City University, Osaka, Japan. 2Faculty of Science, Tokyo University of Science, Tokyo, Japan. 3FIRST-Quantum Information Processing Project, Tokyo, Japan. Synchronised motion between protons and electrons is an important event in chemistry and biology. Such electron-driven proton transfer is a key step in certain biological sys-tems associated with ATP synthesis by using active proton pumps as well as through the conduction of electrons by cytochrome c in living matter[1,2,3]. In quest of molecular quantum functionalities, quantum cooperative phenomena associated with the synchro-nised proton-electron transfer (synchronised PET) have attracted considerable attention from a viewpoint of the multi-functionality. Biimidazolate metal complexes can afford various types of coordination networks in which “complementary” hydrogen bonds be-tween the biimidazolate ligands are involved [4]. Some types of the complexes provide us with models for the understanding of quantum cooperative functionalities such as PET-mediated molecular ferroelectricity. We focus on the generation of ferroelectric or-dered state of biimidazolate dinuclear Rhenium complexes at low temperatures, which is asso-ciated with the synchronized PET. Figure 1 depicts the molecular structure of a complex, [ReIIICl2(PnPr3)2 (Hbim)][ReIVCl2(PnPr3)2(bim)] 1, in which the 2,2’-biimidazolate ligands are connected by the hydrogen-bond. We attempted to characterize the relevant mixed-valence states of the dinuclear complexes by X-ray/neutron diffraction crystal analyses and single-crystal ESR spectroscopy at low temperatures, and quantum chemical calculations of the magnetic tensors appearing in the spin Hamiltonian. In this work the PET behaviour in bulk crystals has been found and identified for the first time. [1] M. Y. Okamura and G. Feher, Annu. Rev. Biochem. 1992 (61) 861-896. [2] P. J. P. Williams, Nature 1995 (376) 643. [3] S. Iwata, C. Ostermelter, B. Ludwig and H. Michel, Nature 1995 (376) 660-669. [4] M. Tadokoro, K. Nakasuji et al., Angew. Chem. Int. Ed. 2007 (46) 5938-5942.

Figure 1. Molecular structure of bimid-azolate dinuclear complex 1.

P7 Takeji Takui

A pulse sequence study for adiabatic quantum computations in molecular spin quantum computers S. Yamamoto1, S. Nakazawa1, 2, K. Sugisaki1, 2, K. Sato1, 2, K. Toyota1, 2, D. Shiomi1, 2, M. Kitagawa2,3 and T. Takui1, 2 1Graduate School of Science, Osaka City University, Osaka, Japan. 2FIRST-Quantum Information Processing Project, JSPS, Tokyo, Japan. 3Graduate School of Engineering Science, Osaka University, Toyonaka, Japan. A molecular spin quantum computer uti-lizes molecular spins, in which electron spins as bus qubits are manipulated by electron spin resonance (ESR) techniques while nuclear spins topologically connect-ed are client qubits. In this work, we have focused on adiabatic quantum computa-tions [1], where the coherence of elec-tronic spins and nuclear ones are manipu-lated in a fully controlled manner. Here, we have investigated an experimental approach to an adiabatic factorization prob-lem of 21 [2] for molecular spin quantum computers. In this quantum algorithm, the op-eration is described by the time evolutions of the Hamiltonian (Eq 1), where is the initial Hamiltonian and is the final one.

Eq 1 The ESR Hamiltonians of a phthalocyanine system (Eq. 2, Fig. 1a) and a diphenyl ni-troxide system (DPNO, Eq. 3, Fig. 1b) are adopted as a three-electron system and a one-electron and two-nuclear system, respectively. Eq 2 Eq 3 In Eqs. 2 and 3, the isotropic interactions are assumed between the spins. As a result, we implemented the pulse sequences for the factorization and estimated the required time and total rotational angles. The evolution time with the ESR Hamiltonian of the DPNO system is five times longer and the total rotational angle of it is twice larger than the phtalocyanine system. Because of the rotational angle of the nuclei, we have also found that the rotating time of nuclei is expected to affect the required time. [1] E. Farhi, J. Goldstone, S. Gutman, M. Sipser, arXiv:quant-ph/0001106. [2] X.-H. Peng, Z. Liao, N. Xu, G. Qin, X. Zhou, D. Suter, J. Du, Phys. Rev. Lett. 2008

(101) 220405.

Fig 1. a) A phtalocyanine system (left) and b) a DPNO system (right)

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Rapid scan electron paramagnetic resonance B.G. Breeze1, B. L. Cann2, M.E. Newton1, 1University of Warwick, Coventry, CV4 7AL UK. 2DTC Research Centre, Belmont Road, Maidenhead, Berkshire, SL6 6JW, UK. Rapid scan electron paramagnetic resonance (RS-EPR) can deliver dramatic sensitivity improvements compared to traditional slow passage EPR. An RS-EPR response is pro-duced when an external magnetic field is swept through the line width of an individual spin packet in a time that is quick compared to the relaxation times. Unmodulated RS-EPR has been used to study the lineshapes of spin labels without the broadening associ-ated with modulation [1]; sweep rates of 8 MG/s have also been used in in vivo EPR imaging and low fields [2]. Here we outline the key benefits offered by field modulated RS-EPR, which can be ob-tained by using a function generator in conjunction with a current amplifier and sweep coils to generate sweep rates up to a few kG/s. The quantitative study of paramagnetic defects in near perfect single crystal samples has many challenges. The available shape and size of the sample often limits the filling factor, reducing absolute sensitivity. Long relaxation times require impracticably low microwave powers to avoid saturation; these may not be achievable on conventional spectrometers and will lead to unreasonably long acquisition times. RS-EPR can also provide an increase in signal to noise com-pared to pulsed techniques where long relaxation times necessitate long shot repetition times. It has been demonstrated that RS-EPR is quantitative and more accurate than slow passage EPR over a wide range of concentrations. Since RS-EPR is a relaxation related response, it is possible to extract information about relaxation times from the parameters required to record the signal. It is also possible to use this technique to separate the signals of separate paramagnetic systems with spectra overlapping field positions but different relaxation times. Support from EPRSC Integrated Magnetic Resonance Centre for Doctoral Training (www.imr-cdt.ac.uk) and De Beers UK is gratefully acknowledged. [1] A. Kittell, T. Camenisch, J. Ratke, J. Sidabras, J Hyde, Detection of undistorted con-tinuous wave electron paramagnetic resonance spectra with non-adiabatic rapid sweep of the magnetic field.Journal of Magnetic Resonance, 2011 (211), 228-33. [2] R. Quine, M. Tseitlin, D Mitchell, G. Eaton, S. Eaton, A Resonated Coil Driver for Rapid Scan EPR, Concepts Magnetic Resonance Part B (Magnetic Resonance Engineer-ing), 2012, 95-110.

P9 Ben Breeze “Rapid scan electron paramagne5c resonance”

Optically Generated Molecular Spin States as Qubits Naitik Panjwani1, 2, Julien Kelber1, 3, Harry L. Anderson3, John J. L. Morton1, 4

1. London Centre for Nanotechnology, University College London, London, UK 2. Department of Physics & Astronomy, University College London, London, UK

3. Department of Chemistry, University of Oxford, Oxford, UK 4. Department of Electronic & Electrical Engineering, University College London, London,

UK

Abstract: Nuclear and electron spins are considered to be robust candidates for quantum bits (qubits), which are the building blocks for quantum computers. Nuclear spins are advantageous as qubits due to their long coherence times, however they also have the disadvantage of exhibiting slow spin interactions and weak thermal polarisation under experimentally accessible conditions1. A coupled electron spin can be used to overcome this limitation, polarise nuclear spins and create fast single qubit gates. The permanent presence of an electron spin, however, can significantly reduce the nuclear spin coherence time1. Recent work has examined optically excited transient electron spins to hyperpolarize, couple and measure nuclear spins at certain key times in order to minimise the long-‐term impact on nuclear spin decoherence. Spin qubits have been studied through pulsed electron paramagnetic resonance (EPR) and double resonance methods (ENDOR) combined with pulsed laser excitation, for the extraction of the Hamiltonian and dynamic parameters. In particular, studies have been performed on fullerene

, using an electron spin triplet to perform fast entangling gates between nuclear spins bonded to the fullerene cage1,2. The lifetime of the optically excited triplet states can limit the fidelity of quantum operations, thus current work involves the study of longer lived and ordered systems. This includes charge-‐separated states created by photo-‐induced charge separation in Donor-‐Bridge-‐Acceptor molecules and crystal structures with longer recombination times to achieve higher fidelity operations. I will describe progress towards using charge-‐separated states as sources of long-‐lived optically-‐generated electron spins, to interact with nuclear spins and mediate couplings between them.

1. Filidou, V. et al. Ultrafast entangling gates between nuclear spins using photoexcited triplet states. Nat. Phys. 8, 596 600 (2012).

2. Schaffry, M. et al. Entangling Remote Nuclear Spins Linked by a Chromophore. Phys. Rev. Lett. 104, 200501 (2010).

P10 NaiAk Pajwani “Op5cally Generated Molecular Spin States as Qubits”

Kinetics of polarization of NV centres in diamond C. Vallotto1, B. G. Breeze1, M. W. Dale1, C. J. Wedge1, M. E. Newton1

1Department of Physics, University of Warwick, UK Negatively charged nitrogen vacancy centres (NV ) in diamond have been extensively studied in the last decade. The NV centre consists of a lattice vacancy, for which one of the nearest neighbour carbon atoms is substituted by a nitrogen atom and an electron is trapped in the vacancy. Through use of optical excitation it is in fact possible to spin-polarize NV centres, giving rise to large population differences which can be easily detected with electron paramagnetic resonance (EPR) spectroscopy. Thanks to remarkable properties such as long spin coherence, optical readout and the possibility to optically polarize the electron spin state, this defect has shown potential applications in many fields such as quantum computation [1], nanoscale magnetometry [2], and as a biological label in bioimaging [3]. Here we report the investigation by means of time-resolved EPR spectroscopy of the temperature dependence of the decay of electron spin polarization of the NV centres produced by optical excitation with a Nd:YAG pulsed laser at 532 nm. Our studies provide information on the fundamental quantum limit of NV based quantum technologies. We would like to acknowledge the Centre for Analytical Science Innovative Doctoral Programme (CAS-IDP) for funding. [1] P. C. Maurer et al., Science, 2012 (336), 1283-1286. [2] G. Balasubramanian et al., Nature, 2008 (455), 648-651. [3] L. P. McGuinness et al., Nat. Nanotechnol., 2011 (6), 358-363.

Figure 1. Structure of the NV centre in diamond.

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Metal-nitroxide systems studied with PELDOR at X-band A. Giannoulis, B.E. Bode EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews PELDOR is a powerful spectroscopic technique for determining distances (2-8 nm), particularly useful in structural biology, where via site directed spin labelling (common-ly nitroxides, NO) the distance of the labels can provide great in-sight on the structure of the system under study [1]. In many metallopro-teins, paramagnetic met-al ions act as cofactors determining the activation and regulation of the biological sys-tem. PELDOR studies of systems containing paramagnetic metal centres are rare due to the metal’s intrinsic challenging properties, i.e. pronounced anisotropy, fast relaxation properties, strong ESEEM effects arising from the interaction of the metal’s unpaired electron with its nuclear spin and in some cases strong orientation selection [2, 3]. Thus, model systems bearing paramagnetic metal centre (i.e. Cu2+, Co2+) and NOs (Figure 1) were synthesized and studied. Relaxation time measurements of the metal and the NO at a range of temperatures for optimizing PELDOR conditions and initial distance meas-urements will be presented. We plan to investigate relaxation filters to separate the dif-ferent paramagnetic species whose spectra overlap [4]. Studies of a reference sample with a diamagnetic metal ion (Zn2+) [3] will provide information on the extend of the contribution of the paramagnetic metal ion in the total PELDOR signal. This work is supported by EPSRC and REA. [1] G. Jeschke, DEER distance measurements on proteins, Annu. Rev. Phys. Chem., 2012 (63), 419-446. [2] B. E. Bode, J. Plackmeyer, M. Bolte, T. F. Prisner, O. Schiemann, PELDOR on an exchange coupled nitroxide copper(II) spin pair, J. Organomet. Chem. 2009 (694) 1172-1179. [3] M. Ezhevskaya, E. Bordignon, Y. Polyhach, L. Moens, S. Dewilde, G. Jeschke, S. van Doorslaer, Distance determination between low-spin ferric haem and nitroxide spin label using DEER: the neuroglobin case, Mol. Phys., 2013 (111) 2855-2864. [4] J. H. van Wonderen, D. N. Kostrz, C. Dennison, F. MacMillan, Refined distances between paramagnetic centers of a multi-copper nitrite reductase determined by pulsed EPR (iDEER) spectroscopy, Angew. Chem. Int. Ed., 2013 (52) 1990-1993.

Figure 1. Model systems synthesized and studied.

P12 Angeliki Giannoulis “Metal-‐nitroxide systems studied with PELDOR at X-‐band”

PELDOR distance measurements: quantification of artefacts in multi-spin systems S.Valera, B. E. Bode

EaStCHEM School of Chemistry, Biomedical Sciences Research Complex and Centre of Magnetic Resonance, University of St Andrews PELDOR (Pulsed Electron-Electron Double Resonance) is an emerging technique for nanomentre distance measurement in nano-sized clusters between specific sites of molecules [1]. Most commonly nitroxide radicals are used as probes for EPR distances because they are easy to introduce in biological systems such as proteins or nucleic ac-ids [2]. PELDOR distance measurements currently rely on DeerAnalysis [3] as the gold standard for distance distributions. In the presence of more than two unpaired electrons the dipo-lar coupling is affected by sum and difference frequencies which introduce additional peaks in distance distributions [4-6]. Oth-er factors which may contribute to broadening and artefacts are orientation selection and deuterium ESEEM oscilla-tions when using deuterated solvents [7]. In this work we explored a range of measurement parameters and sample matrices which partially suppress arte-facts in distance distributions. Studies are performed on newly synthesised model systems containing two, three or four nitroxide moieties. Model systems are de-signed to be rigid, rod-like and exhibit high symmetry for minimising the number of distances. This work is supported by a grant from Marie Curie Actions and EPSRC. [1] Schiemann O., Prisner T. F., Quart. Rev. Biophys., 2007, 40, 1-53. [2] Jeschke G., Polyhach Y., Phys. Chem. Chem. Phys., 2007, 9, 1895-1910 [3] G. Jeschke, V. Chechik, P. Ionita, A. Godt, H. Zimmermann, J. Banham, C. R. Timmel, D. Hilger, H. Jung, Appl. Magn. Reson., 2006, 30, 473-498 [4] von Hagens T., Polyhach Y., Sajiid M., Godt A., Jeschke G., Phys. Chem. Chem. Phys., 2013, 15, 5854-5866 [5] Giannoulis A., Ward R., Branigan E., Naismith J. H., Bode B. E., Mol. Phys., 2013, 111, 2845-2854 [6] Bode B. E., Margraf D., Plackmeyer J., Dürner G., Prisner T. F., Schiemann O., J. Am. Chem. Soc., 2007, 129, 6736-6745 [7] Jeschke G., Annu. Rev. Phys. Chem., 2012, 63, 419-446

Figure 1. Changes in distance distributions of a tetrahedral tetra-radical related to the variation of inversion effi .

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Studying the conformational dynamics of HD-PTP by site-directed spin labelling and double electron-electron resonance Graham Heaven1,2, Alistair J Fielding1, Lydia Tabernero2, Philip Woodman2

1Photon Science Institute, University of Manchester, United Kingdom. 2Faculty of Life Sciences, University of Manchester, Manchester, United Kingdom. HD-PTP is an important protein in the sorting of epidermal growth factor receptor (EGFR) to intralumenal vesicles of multivesicular bodies in the human cell [1]. This is a key step in the downregulation and degradation of activated EGFR, which can cause excessive cell proliferation and tumour growth if overstimulated [2]. The biological function of HD-PTP homolog ALIX has been shown to be dependent on significant rearrangement of its V domain which can exist in either an open or closed conformation (Figure 1). HD-PTP V domain contains only three cysteine residues, making it an ideal candidate for electron paramagnetic studies using spin labelling. Recombinant HD-PTP V domain has been cloned and expressed in E.coli. Site-directed mutagenesis and spin-labelling with allow investigation using double electron-electron resonance (DEER) experiments. The dynamics of the V domain in the presence of interacting partners will also be investigated to infer functional relationships and a mechanism of regulation. This work will help understand the function of HD-PTP in this important aspect of cell regulation. [1] N. Ali, L. Zhang, S. Taylor, A. Mironov, S. Urbé, and P. Woodman, Curr. Biol.,

2013, 23, 453 461. [2] L. K. Goh, F. Huang, W. Kim, S. Gygi, and A. Sorkin, J. Cell Biol., 2010, 189,

871 883. [3] N. Pashkova, L. Gakhar, S. C. Winistorfer, A. B. Sunshine, M. Rich, M. J.

Dunham, L. Yu, and R. C. Piper, Dev. Cell, 2013, 25, 520 533. [4] L. Sangho, J. Anjali, N. Kunio, EO. Freed and JH. Hurley, Nat. Struct. Mol. Biol.,

2007, 14, 194-199.

Figure 1. HD-PTP structural homolog ALIX exists in either an open (left, PDB: 4JJY [3]) or closed (right, PDB: 2OJQ [4]) conformation.

P14 Graham Heaven “Studying the conforma5onal dynamics of HD-‐PTP by site-‐directed spin labelling and double electron-‐electron resonance”

The use of EPR Spectroscopy as a Predictive Tool for Pharmaceutical Formulation Development H. Williams1, A. Rengner2, N. Akhtar1, J. Booth1 and C. Caulfield1

1Product Development, AstraZeneca, Silk Road Business Park, Macclesfield, Cheshire, UK, SK10 2NA. 2King’s College London, School of Biomedical and Health Sciences, Franklin-Wilkins Building, 150 Stamford Street, London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P15 Helen Williams “The use of EPR Spectroscopy as a Predic5ve Tool for Pharmaceu5cal Formula5on Development”

GPa uniaxial stress of single crystal samples M.W. Dale1, B.G. Breeze1, B.L. Cann2, B.L. Green3, M.E. Newton1 1Department of Physics, University of Warwick, Coventry, CV4 7AL, UK. 2De Beers Technologies UK, Belmont Road, Maidenhead, SL6 6JW, UK 3Element Six Ltd, Global Innovation Centre, Fermi Avenue, Harwell Oxford, OX1 0QR, UK. Uniaxial stress is commonly used in optical absorption and photoluminescence studies of colour centres in single crystal diamond providing valuable information about their symmetry and electronic structure. Uniaxial and hydrostatic pressures have been suc-cessfully combined with electron paramagnetic resonance (EPR), for instance to study single crystals [1] and proteins [2], but the maximum pressures attained have so far been insufficient for studying diamond. To overcome the challenges a new uniaxial stress EPR probe capable of GPa pressure at the sample has been constructed. The pressure on the sample is proportion-al to the sample cross-section therefore it is desirable to use small samples to achieve the high pressures re-quired. To maintain absolute EPR sensitivity a loop-gap resonator is used. In the new probe stress is applied to the sample by pressurised gas acting on a piston with the force transmitted to the sample by quartz rods and diamond anvils (See Figure 1). The probe is compatible with standard cryostats allowing operation down to helium temperature and allows for illumination of the sample and optically detected EPR. The authors gratefully acknowledge the support of De Beers Technologies UK, the iMR-CDT, EPSRC and QINVC for this project.

[1] T.W. Kool et al. Jahn–Teller and off-center defects in BaTiO3: Ni+, Rh2+, Pt3+ and Fe5+ as studied by EPR under uniaxial stress. J. Phys. Condens. Matter 19, 496214, 2007.

[2] J. McCoy & W.L. Hubbell, High-pressure EPR reveals conformational equilibria and volumetric properties of spin-labelled proteins, PNAS 108(4), 1331–6, 2011.

Figure 1. Illustration of a sample situated in the loop gap resonator between diamond anvils. A cross section has been taken of the loop gap for illustrative purposes.

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Spin probing of the fast protonation reactions with semiquinone radicals A.S.Masalimov, S.N.Nikolskiy, A.A.Tur Karaganda State University, Kazakhstan, [email protected]

The stable semiquinone radicals 3,6-di-tert.butyl-2-oxyphenoxyl (I), 4,6-di-tert.butyl-3-clorine-2-oxyphenoxyl (II) and 4-triphenylmethyl-6-tert.butyl-3-clorine-2-oxyphenoxyl (III) was used as acid spin probe (XH) for investigations of kinetic basicity of different proton-acceptors (Y): tertiary amines, alkaloids, nitrogen heterocycles etc in medium of organic solutions:

This spin probes also allow to study the kinetic of fast intermolecular proton exchange (IPE) reactions between XH and several H-acids: carbon acids, primary and secondary amines (YH):

It is necessary to say that the high intramolecular mobility of hydroxilic hydrogens atom in semiquinone radicals I - III determine the nanosecond homolytic tautomerism. Therefore radicals I – III have property of the dual protolytic reactivity. With a glance of tautomerism the general scheme of intermolecular proton transfer reactions for spin semiquinone probes represents as:

If for spin probe I intramolecular tautomerism A ! A’ will be degenerate process and both canals of intermolecular proton transfer (IPT) reactions are equivalent, but in stable radicals II and III it has nongenerate character, since oxyphenoxyls have the different structure of initial (A), final (C) products and intermediates (B). Besides the rates constants of fast IPT and IPE reactions 1-3 were determined the kinetic and thermodynamic parameters of intramolecular hydrogen-transfer, solvation radicals I - III and kation-transfer in corresponding ion-pairs C by EPR-spectroscopy.

P17 Sergey Nikolskiy “Spin probing of the fast protona5on reac5ons with semiquinone radicals”

Quantifying the sensitivity of HiPER, the W-Band High Power Pulsed Spectrometer. C. Motion, P.A.S. Cruickshank, D. Bolton, R.I. Hunter, H. El Mkami, G.M. Smith1

1Millimeter Wave and High Field EPR Group, School of Physics & Astronomy, Univer-sity of St Andrews. Ensuring sufficient sensitivity in EPR experi-ments is essential if one wishes to obtain accu-rate results in a timely manner on low concen-tration samples. At St Andrews we have been working to im-prove and quantify the concentration sensitivity of a home-built wideband W-Band spectrome-ter, relative to that of an Elexsys X-Band Bruker system using a MD4 cavity (the X-band cavity with the highest concentration sensitivity). For experiments relevant for PELDOR we have seen enhancements of up 100 fold for W-Band (Fig-ure 1) compared to X-band (Figure 2) in spin echo experiments. However, more typical re-peatable enhancements are approximately 30 fold, for the same sample and sample volume. This level of increase in sensitivity allows PELDOR experiments to be carried out more quickly or with longer time windows or at lower sample concentrations. It also makes experi-ments to determine the relative orientation of rigid spin labels practical (Orientational PELDOR). This paper will discuss the various methods that have been employed to provide this sensitivity increase, including the use of new FEP sample tubes, improved cavity matching and improved annealing and glassing protocols. Various applications will be discussed in the paper. [1] Cruickshank, P. A. S. et al. A kilowatt pulsed 94 GHz Electron Paramagnetic Reso-nance Spectrometer with high concentration sensitivity, high instantaneous bandwidth, and low dead time. Rev. Sci. Instrum. 80, 103102 (2009).

Figure 1. Spin Echo 1µM TEMPO at W-Band, measured using HiPER.

Figure 2. Spin Echo 1µM TEMPO at X-Band, using MD4 cavity for PELDOR.

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An investigation into the suitability of Rx as a spin label for orientation studies using W-band pulsed electron paramagnetic resonance (PELDOR). M. Stevens1, J. McKay2, H. El-Mkami2, J. Robinson1, G. Smith2, D. Norman1

1School of Life Sciences, University of Dundee, Dundee, Uk 2School of Physics and Astronomy, University of St Andrews, St Andrews, Uk !

The use of pulsed electron double resonance (PELDOR) for measuring orientations in proteins requires one to incorporate spin labels that are both conformationally restricted and defined in their spatial relationship to the underlying protein structure. The Rx bifunctional spin label would seem to fit the first criteria [1] in that the double attachment site would be expected to restrict the conformational space that the label could explore. We have preformed a systematic study of the Rx label attached to all possible secondary structural position-types and attempted to determine the label conformation and dynamics. Using molecular dynamics backed up by both CW and PELDOR experimental

studies, we have attempted to characterize and define the conformational and structural behavior of these spin-label constructs. The use of orientation measurements in structural refinement requires an understanding of the spin-label conformation and structure, in relation to the underlying protein. To test our understanding of spin label conformation, we have constructed mutations in "#$%&'()$"% residues and show that the system indeed can behave in a predictable manner. The most defined and restricted sites have been used to measure spin-label orientation at W-band. We have gone on to demonstrate the use of orientation restraints in structural refinement.

1. Fleissner, M.R., et al., Structure and dynamics of a conformationally constrained nitroxide side chain and applications in EPR spectroscopy. Proceedings of the National Academy of Sciences, 2011.

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Deuteration impact on the electron spin-echo (ESE) decay of double spin labelled proteins. Richard Ward1, Andrew Bowman2, Doaa Kredi2, Tom Owen-Hughes2, David G. Nor-man2, Hassane El Mkami3

1University of St-Andrews, BMS building, North haugh, St-Andrews, Fife, KY16 9ST. 2School of life Science, University of Dundee, Dundee DD1 5EH, UK. 3University of St-Andrews, School of Physics and Astronomy, North Haugh, St-Andrews, Fife, KY16 9SS, UK. Abstract In order to elucidate the impact of the deuteration on electron spin relaxation rates, two different proteins have been studied at X and W-band: the histone core octamer which was segmentally deuterated and POTRA domain with high deuteration efficiency (see figure-1 and -2). Both proteins are double spin-labelled. The results have shown that the deuteration has not only lengthened the relaxation time Tm but also enhanced the elec-tron dipole-dipole interaction in the routine two-pulse electron spin echo (ESEEM).

Figure-1: A) Two rotated views showing the position of the spin label on histone H3 (blue surface), histone H4 shown by magen ta surface and H2a-H2b shown by green cartoon, B) Crystal structure of POTRA domains 1 and 2.

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PELDOR on highly-symmetric multimeric membrane proteins C. Pliotas1, R. Ward1, Akiko Rasmussen2, I. R. Booth2, Olav Schiemann3 and J. H. Naismith1

1 Centre for Biomolecular Sciences, University of St Andrews, St Andrews, UK. 2Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK. 3 Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn, Germany Mechanosensitive channels are highly symmetric and multimeric integral membrane proteins which span across all kingdoms of life. The most well-characterised of these systems, are MscS and MscL. MscS forms a homoheptamer and MscL a homopentamer. PELDOR application on these complex systems has been a challenge due to the presence of inherent multiple distances, that give rise to multispin effects. In two recent studies, distance measurements between nitroxide spin labels have been made possible, while MscS was in detergent solution [1] and/or embeded in lipid bilayer mimics [2]. Both studies concluded that the x-ray crystal structures constitute the most reliable guide to accurately describe MscS conformational state, under all conditions tested. However, structural analysis took into consideration only the first distance (D1-2) since concerns have been raised to the reliability and accuracy of both second (D1-3) and third (D1-4) distances appearing in the distance distribution profile, because it is believed that these are distorted by multispin effects. We report a new MscS high-resolution spin-labelled structure with the seven spin labels resolved, which allows a direct comparison of the x-ray with the PELDOR spin-to-spin derived mean distances, in agreement with our previous study [1]. Further, data with the pentameric membrane protein channel MscL reconstituted in lipid mimics such as lipo-somes, nanodiscs and bicelles, are also presented, demonstrating the high potential of PELDOR distance measurements for such complex multi-spin systems within a lipid native-like environment. This work is funded by BBSRC. [1] C. Pliotas, R. Ward, E. Branigan, A. Rasmussen, G. Hagelueken, H. Huang, S. S. Black, I. R. Booth, O. Schiemann, J. H. Naismith, Conformational state of the MscS mechanosensitive channel in solution revealed by pulsed electron-electron double reso nance (PELDOR) spectroscopy. Proceedings of the National Academy of Sciences USA. 2012 (109) 2675-2682. [2]R. Ward, C. Pliotas, E. Branigan, C. Hacker, A. Rasmussen, G. Hagelueken, I. R. Booth, S. Miller, J. Lucocq, J. H. Naismith, O. Schiemann, Probing the Structure of the Mechanosensitive Channel of Small Conductance in Lipid Bilayers with Pulsed Electron-Electron Double Resonance. Biophysical Journal. 2014 (in press).

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Water mediated triplet-triplet energy transfer: a common feature of the photoprotective site in different peridinin-chlorophyll-proteins M. Albertini1, C.E. Tait2, M. di Valentin1 and D. Carbonera1

1Dipartimento di Scienze Chimiche , Università degli Studi di Padova, Italy. 2Centre for Advanced Electron Spin Resonance, Department of Chemistry, University of Oxford, UK. The photoprotection process plays a pivotal role in photosynthetic systems disposing of the excess en-ergy coming from the sun and de-activating highly hazardous species which can damage the sensitive and finely tuned photosynthetic apparatus. Triplet-triplet energy transfer (TTET) represents one of the major photoprotective pathways working in the light-harvesting complexes, the very first light an-tennas of the entire photosynthetic process. TTET consists of a double electron transfer between a couple of partners described by Dex-

anism, and it is characterized by a rate constant depending on the exchange integral between the wavefunctions of the transferred electrons. For this rea-son relative orientation and distance of the partners (chlorophyll and carotenoid respec-tively) plays a crucial role in influencing the effectiveness of the photoprotection itself. The antenna complex Peridinin-Chlorophyll a-Protein (PCP) from Amphidinium carte-rae has been widely investigated via advanced electron spin resonance spectroscopy. Unambiguous identification of the photoprotective site (Chl601-Per614 according to the original nomenclature) has been provided[1] together with the evidence that a structured water molecule at the interface between the two partners is involved in the TTET mechanism[2]. In this study, the same approach based on electron spin echo envelope modulation (ESEEM) spectroscopy combined with in-silico calculations has been ap-plied to characterize the photoprotective site of three different PCP antennas namely High-Salt PCP, BChl-reconstituted PCP and PCP from Heterocapsa pygmaea. The re-sults indicate that the ordered water molecule is always present with a conserved orien-tation of the hyperfine tensor with respect to the molecular framework of the photopro-tective pair of pigments among all the systems investigated. This strong evidence sug-gests that this water molecule is a decisive and integral part of the entire photoprotective system and it can be of fundamental meaning for a smart design of systems that can both efficiently harvest light and photoprotect against excessive light irradiation. [1] M. Di Valentin, S. Ceola, E. Salvadori, G. Agostini, D. Carbonera, Identification by time-

resolved EPR of the peridinins directly involved in chlorophyll triplet quenching in the pe-ridinin-chloropyll a-protein from Amphidinium carterae, 2008 (1777) 186-195

[2] M. Di Valentin, C. Tait, E. Salvadori, L. Orian, A. Polimeno, D. Carbonera, Evidence for water-mediated triplet-triplet Energy transfer in the photoprotective site of the peridinin-chlorophyll a-protein, Biochim. Biophys. Acta Bioenerg. 2014 (1837) 85-97

The photoprotective site of PCPA.c.: peri-dinin 614, chlorophyll 601, and water.

P22 Marco AlberAni “Water mediated triplet-‐triplet energy transfer: a common feature of the photoprotec5ve site indifferent peridinin-‐chlorophyll-‐proteins”

Structural conformations of XPD and XPB helicases studied by PELDOR Diana Constantinescu Aruxandei1, Biljana Petrovic-Stojanovska1, Hassane El Mkami2, Olav Schiemann3, James H. Naismith1, and Malcolm F. White1 1Biomedical Science Research Complex, University of St Andrews, St Andrews, UK 2School of Physics and Astronomy, University of St Andrews, St Andrews, UK 3Institute of Physical and Theoretical Chemistry, University of Bonn, Bonn, Germany XPD and XPB are key enzymatic components of the tran-scription factor TFIIH, essential in Nucleotide Excision Re-pair (NER) and transcription initiation. TFIIH catalyses DNA opening at promoters during transcription initiation and at DNA lesions in NER pathway. Because of the com-plexity of the TFIIH system, the individual functions of eu-karyal XPD and XPB are difficult to study at the molecular level. The archaeal homologues have proven to be good model systems. Although there are three crystal structures of the apo form of archaeal XPD, one of a XPD-4 nucleotides DNA [1] and one of apo XPB [2], the mechanism of action and the conforma-tional changes that accompany it are still not clear. Moreo-ver, the crystal structure of XPB is questionable in terms of the in vivo relevance, due to the absence of the binding part-ners. A canonical conformation that was proposed for the DNA-bound form might exist also in absence of DNA. Here we investigated the structures of XPD and XPB and the conformational changes induced by DNA using X-band and W-band (HiPER) PELDOR. Two examples of dipo-lar evolution of the apo forms are shown in Figure 1. The XPD distances between do-mains seem to vary slightly compared to the crystal structure (within 2-4 Å) and there is no significant change when DNA is present. XPB shows high flexibility between the relevant domains, indicated by the absence of a clear oscillation. This can also explain the previous published crystal structure. A more rigid double mutant (Fig. 1) measured at 94 GHz indicates that the crystal conformation represents only a small population in solution. The DNA induces a closure of XPB that results in a 3 Å shorter distance. This work is supported by a Welcome Trust grant. [1] J. Kuper et al., Functional and structural studies of the nucleotide excision repair

helicase XPD suggest a polarity for DNA translocation, EMBO J, 2012 (31), 494. [2] L. Fan et al., Conserved XPB Core Structure and Motifs for DNA Unwinding: Im-

plications for Pathway selection of Transcription or Excision Repair, Mol. Cell, 2006 (22) 27.

Figure 1. PELDOR dipo-lar evolution of XPD and XPB helicases

P26 Diana Aruxandei “Structural conforma5ons of XPD and XPB helicases studied by PELDOR”

Biophysical, mutational and functional investigation of the chromo-phore-binding pocket of light-oxygen-voltage photoreceptors Ralph P. Diensthuber1, Christopher Engelhard2, Nora Lemke1, Tobias Gleichmann1,3, Robert Ohlendorf1, Robert Bittl2,*, Andreas Möglich1 1Humboldt-Universität zu Berlin, Institut für Biologie, Biophysikalische Chemie, Berlin, Germany. 2Freie Universität Berlin, Fachbereich Physik, Institut für Experimentalphysik, Berlin, Germany. As light-regulated actuators, sensory photoreceptors underpin optogenetics and numerous applications in synthetic biology [1]. Protein engineering has been applied to fine-tune the properties of photoreceptors and to generate novel actuators. For the blue-light-sensitive light-oxygen-voltage (LOV) photoreceptors, mutations near the flavin chromophore modulate re-sponse kinetics and the effective light responsive-ness. Here, the mobility of the flavin's C8! methyl group – which can be favourably stud-ied by EPR spectroscopy – provides a conven-ient proxy for studying the effect of such mu-tations on the flavin binding pocket. Investi-gation vairous mutants in the artificial photore-ceptor YF1 [2] as well as their analogs in the LOV2 domain from Avena sativa phototropin 1 identified cor-related effects on chromophore environment as probed by pulsed ENDOR spectroscopy and response kinetics as probed by optical spectroscopy. These results demonstrate that, when carefully chosen, mutations provide a powerful means to adjust the light-response function of photoreceptors as demanded for diverse applications. Funding through a Sofja-Kovalevskaya Award by the Alexander-von-Humboldt Foundation (A.M.), by Deutsche Forschungsgemeinschaft within FOR1279 (A.M.) and within the Cluster of Excellence in Ca-talysis ‘UniCat’ (R.B.) is gratefully acknowledged. [1] Deisseroth, K., Feng, G., Majewska, A. K., Miesenböck, G., Ting, A., and Schnitzer, M. J. Next-

generation optical technologies for illuminating genetically targeted brain circuits. Journal of Neu-roscience, 2006 (26) 10380-10386

[2] Diensthuber, R. P., Bommer, M., Gleichmann, T., and Möglich, A. Full-length structure of a sensor histidine kinase pinpoints coaxial coiled coils as signal transducers and modulators. Structure 2013 (21), 1127–1136.

Figure 1. Top: Mobile C8! peak in pulsed ENDOR spectra of YF1 mutations (green: WT, blue: L82I, red: N37C, black: both) as a function of temperature. Bottom: Corre-lation between midpoint temperature for the C8! mobile " immobile transition and protein's dark recovery rate for YF1 vari-ants (#) and AsLOV2 variants ($).

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Electrically detected magnetic resonance (EDMR) of a-Si:H, toward possible EDMR standard samples Stephen C. Hogg, Stephen Reynolds and David J. Keeble

Division of Physics, SUPA, School of Engineering, Physics, and Mathematics, Universi-ty of Dundee, Dundee DD1 4HN, UK. Electrical detected magnetic resonance (EDMR) detects spin-dependent transitions di-rectly involved in a charge transport process this can be a commercial electronic device or it can be a custom-fabricated sample with high quality electrical contacts. The necessary condition for an EDMR signal is for a contribution of the transport current to result from a spin-dependent process involving the paramagnetic centre or centres, for example due to a recombination or hopping transport process. The method has been transformed more recently by the development of pulsed EDMR (pEDMR) [1], this enables spin coherence to be probed and allows a range of hyperfine spectroscopy techniques to be applied. EDMR can be challenging to perform on a new material or device system; as a conse-quence it can be useful to have a sample with a known spectrum which can allow the spectrometer system to be evaluated. Hydrogenated amorphous silicon (a-Si:H) was one of the first materials systems to be studied by CW-EDMR [2], more recently low tem-perature pEDMR has also been observed [3]. Here we report CW and pEDMR meas-urements on a-Si:H thin films with simple Al contacts. The geometry of the contacts has been systematically varied and the dependence on the EDMR as a function of applied bias studied. All measurements were performed at room temperature. Samples with interdigitated top contacts, similar to those previously reported [1], were found to markedly increase a-Si:H EDMR signal intensities and reduce operating volt-ages. Illumination is required, and the well-known decay then stabilisation of the oper-ating current with illumination time, the Staebler-Wronski effect, must also be accom-modated in the measurement protocol. Nevertheless, it has been found that the room temperature signal strength and operating conditions make these simple a-Si:H c-

suitable reference samples. [1] C. Boehme and K. Lips, Electrical detection of spin coherence in silicon, Phys.

Rev. Lett. 91, 246603 (2003). [2] I. Solomon, D. Biegelsen, and J. C. Knights, Spin-dependent photoconductivity in

n-type and p-type amorphous silicon, Solid State Commun. 22, 505 (1977). [3] T. W. Herring, S. Y. Lee, D. R. McCamey, P. C. Taylor, K. Lips, J. Hu, F. Zhu, A.

Madan, and C. Boehme, Experimental discrimination of geminate and non-geminate recombination in a-Si:H, Phys. Rev. B 79, 195205 (2009).

P24 Stephen Hogg “Electrically detected magne5c resonance (EDMR) of a-‐Si:H, toward possible EDMR standard samples”

EPR of Fe3+ centres in SrTiO3 David J.A. Finch, Ijaz Ahmad, Adam El-Qmache and David J. Keeble

Division of Physics, SUPA, School of Engineering, Physics, and Mathematics, Univer-sity of Dundee, Dundee DD1 4HN, UK. The substitutional incorporation of Fe3+ ions in SrTiO3 provides the clearest example of charge compensation of an acceptor ion in a perovskite oxide, ABO3, material, and is an established model system for B-site acceptor doping in defect chemistry. Fe3+ substitutes for Ti4+ in cubic phase SrTiO3, either within a complete oxygen octahedron, giving cubic centre [1], or at an octahedron containing a single oxygen vacancy resulting in a centre with marked axial symmetry [2]. There has been a recent resurgence of interest in these centres as they may provide insight on the mechanisms of resistive switching devices, and more generally provide a mechanism for monitoring oxygen vacancy behaviour. De-spite the extensive EPR literature on the Fe3+-VO centre in SrTiO3 the complete spin-Hamiltonian to fourth order in zero field splitting (ZFS) terms has not be unambiguously reported. EPR measurements at 9.5 GHz are reported on a 0.022% Fe-doped SrTiO3 single crystal. A complete roadmap of EPR transitions extending in field to 2 T, and involving the low two Kramer doublet manifolds is obtained. Unambiguous SH parameters to 4th order in ZFS are obtained. Superposition model (SPM) calculations of the ZFS SH parameters are performed and the validity of available Fe3+-O SPM model parameters evaluated. [1] K. A. Müller, Helv. Phys. Acta 31, 173 (1958). [2] E. S. Kirkpatrick, K. A. Müller, and R. S. Rubins, Phys. Rev. 135, A86 (1964).

P25 David Finch “EPR of Fe3+ centres in SrTiO3”

Electrically detected magnetic resonance of MEH-PPV:PCBM solar cell devices Stephen C. Hogg, Stuart A.J. Thomson, Ifor D.W. Samuel and David J. Keeble

Division of Physics, SUPA, School of Engineering, Physics, and Mathematics, Univer-sity of Dundee, Dundee DD1 4HN, UK. Thin film organic semiconductor solar cells have the potential advantage of low-cost, simple, production on a range of substrates. However, the materials used are sensitive to the environment, and photovoltaic efficiencies are lower than those of other thin film photovoltaic technologies. The most efficient configuration is a blend of electron ac-cepting fullerene molecules with a positive carrier transporting organic semiconducting polymer. The resulting device has a high density of interfaces between the two material types and is termed a bulk heterojunction (BHJ). Photons generate excitons which need to separate into their individual charge carriers to allow charge transport to the elec-trodes. The BHJ configuration maximises the separation process; the fullerene network allows efficient transport of the electrons, and the polymer transports the positive carri-ers. The carriers interact with the molecular structures through which they move and so are termed polarons. Electrical detected magnetic resonance (EDMR) detects paramagnetic centres directly involved in a carrier transport process within a device. The contribution to the transport current must be spin-dependent, involving the paramagnetic centre or centres, for ex-ample due to a spin-dependent recombination or hopping transport process. EDMR can be many orders of magnitude more sensitivity than EPR and provides a unique charac-terisation method, it can be performed in CW or pulsed mode [1]. CW and pulsed EDMR measurements have been performed on simple BHJ solar cells comprising poly(2-methoxy-5- -ethyl)-hexoxy-p-phenylene) vinylene (MEH-PPV) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM), similar to those used previous-ly [2]. Both encapsulated and unencapsulated devices were studied, the time evolution of the room temperature EDMR and the associated device current-voltage characteris-tics are reported. Degradation of the I-V characteristic was found to also result in changes to the EDMR. [1] C. Boehme and K. Lips, Electrical detection of spin coherence in silicon, Phys.

Rev. Lett. 91, 246603 (2003). [2] J. Behrends, A. Schnegg, K. Lips, E. A. Thomsen, A. K. Pandey, I. D. W. Samuel,

and D. J. Keeble, Bipolaron Formation in Organic Solar Cells Observed by Pulsed Electrically Detected Magnetic Resonance, Phys. Rev. Lett. 105, 176601 (2010).

P27 Stuart Thomson “Electrically detected magne5c resonance of MEH-‐PPV:PCBM solar cell devices”

Magnetostructural trends in water-bridged dinickel complexes

James P. S. Walsh,1 Stephen Sproules,2 Anne-Laure Barra,3 David Collison,1 Richard E. P. Winpenny1 and Eric J. L. McInnes1

1School of Chemistry and Photon Science Institute, The University of Manchester, Oxford Road, Manchester, M13 9PL, United Kingdom.

2School of Chemistry, Joseph Black Building, The University of Glasgow, University Avenue, Glasgow, G12 8QQ, United Kingdom.

3Laboratoire National des Champs Magnétiques Intenses, 25, rue des Martyrs, B.P. 166, 38042 Grenoble Cedex, France.

Magnetostructural studies on exchanged coupled systems are usually restricted to very simple cases where the ions are well described using spin-only models (no orbital contribution), and/or the exchange interaction dominates over all other interactions (such as zero-field splitting). Magnetostructural studies on dinuclear copper(II) complexes are particularly common because they satisfy both conditions simultaneously. Although such studies often paint a pretty picture, they are rarely relevant in the field of single-molecule magnetism, where a large ground state spin and a large axial anisotropy (D) are vital prerequisites (the latter of these requirements dissuades the use of spin-only ions, since cluster anisotropy is essentially a tensor sum of individual anisotropy terms, and these in turn rely on the presence of an orbital angular momentum). What would be much more useful is an understanding of the important factors governing the exchange interactions between ions possessing a large intrinsic anisotropy.

This poster details a recent study carried out a family of five structurally related water-bridged nickel(II) dimers exhibiting contrasting exchange interactions of a magnitude similar to the zero-field splitting (1–10 cm!1). Powder magnetic measurements combined with high-field (331 GHz) electron paramagnetic resonance and supported by ab initio calculations allow us to extract the sign and magnitude of the exchange interaction in all complexes and relate this parameter to the bonding angle of the bridging water molecule.

P28 James Walsh “Magnetostructural trends in water-‐bridged dinickel complexes”

P29 “Stable, Paramagne5c Flavin Model Iden5fied via its Magne5c Nuclei Using Pulsed EPR “

Stable, Paramagnetic Flavin Model Identified via its Magnetic Nuclei Using Pulsed EPR Alexander T. Murray1, David R. Carbery1, Amgalanbaatar Baldansuren2*, Alistair Fielding2, Floriana Tuna2, David Collison2 1Department of Chemistry, University of Bath, Claverton Down, Bath BA2 7AY 2EPSRC National EPR Service, the Photon Science Institute, School of Chemistry, the University of Manchester, Oxford Road, Manchester M13 9PL Biological cofactors are used in a diverse array of enzymes to promote a great variety of metabolic processes in both prokaryotic and eukaryotic life. In particular enzymatic re-dox chemistry tends to require a cofactor for electron transfer processes, with among the most ubiquitous being flavoenzymes. Indeed, up to 3.5% of all genes encode for flavin-dependent proteins, showing the ubiquity of this functional motif [1]. Flavins are known to exist in three states; oxidised, reduced and the paramagnetic sem-iquinone forms. These have all been well studied in biological systems but in model systems while two electron reductions of cationic flavinium models is known [2], gen-eration of the semiquinone form has not previously been achieved. One of many observed methods of generation of semiquinone flavin in biochemistry is reaction with sulfides such as cysteine and methionine residues in the protein, and so we aimed to see if it were possible to observe electron transfer between a sufficiently elec-tron rich sulfide and bridged flavin model 1, and thus stable paramagnetic species by EPR spectroscopy. The high-resolution pulsed EPR techniques, such as ESEEM and ENDOR, make use of the paramagnetic properties of the heterocyclic flavin to determine hyperfine interac-tions within the flavin molecule itself, via the isotropic and anisotropic couplings with magnetic nuclei, e.g. 14N, 19F, and 1H in this work. Under near cancellation condition at the X-band, the nuclear quadrupole coupling is of the order of k ≈ 0.97 MHz, assigned to the 14N(3)H [3]. The hyperfine coupling is dominated by the isotropic constant of this nitrogen. Analysis of the contour-ridges in (ν12) vs (ν22) coordinates [4] allows direct, simultaneous determination of aiso and T of 19F and 1H. The contribution of exchangea-ble protons was identified using the 1H/2H exchange reaction. [1] Macheroux, P.; Kappes, B.; Ealick, S. E. FEBS J. 2011 (278) 2625. [2] Imada, Y.; Iida, H.; Ono, S.; Murahashi, S.-I. J. Am. Chem. Soc. 2003 (125) 2868. [3] Safin, I. A.; Osokin, D. Ya. Nuclear Quadrupole Resonance in Nitrogen Com-pounds, pp.182-250, Science, Moscow, 1977. [4] Dikanov, S. A.; Bowman, M. K. J. Magn. Reson. Ser. A 1995 (116) 125-128.

P30 “EPSRC Na5onal EPR Research Facility & Service”

EPSRC National EPR Research Facility & Service Eric J. L. McInnes, David Collison, Floriana Tuna, Alistair J. Fielding, Amga Baldansuren and Daniel O. Sells School of Chemistry and Photon Science Institute, The University of Manchester, U.K. The University of Manchester hosts the EPSRC National Facility & Service for electron paramagnetic resonance (EPR; also known as ESR) spectroscopy. EPR can be applied to any material with unpaired electrons, and is of wide application in chemistry, physics, materials, biology and medicine. For example, it is used to probe: •  transition ions, radicals, defects; intrinsic, induced or labelled •  radical identity, geometric and electronic structure •  radical environment/surroundings •  radical dynamics (e.g. viscosity, polarity of medium) •  reaction mechanisms/kinetics •  electron spin dynamics •  structure determination in amorphous materials. The Facility has state-of-the art experimental techniques for multi-frequency EPR and data modeling, including; •  Continuous wave (c.w.) EPR at 1, 4, 9, 24, 34 and 94 GHz frequencies (L-, S-, X-, K-,

Q- and W-band). •  pulsed EPR at 4, 9 and 34 GHz, including ESEEM, ENDOR, DEER (PELDOR) and

HYSCORE methods. •  Collaborative arrangements for pulsed EPR at 94 GHz, very high frequency c.w. EPR

(100 - 750 GHz), and frequency domain EPR. •  “Pump-probe” optical (laser, LED or white light) excitation with transient or pulse

detection •  Electrochemical generation at all frequencies.

P31 How sensi5ve is HIPER for PELDOR?

How sensitive is HIPER for PELDOR?

David Bolton1, Rob Hunter1, Paul Cruickshank1, Hassane El Mkami1, Claire Motion1, Johannes McKay1, Graham Smith1 1School of Physics and Astronomy, University of St Andrews, Scotland HIPER is a high power (1kW) high frequency (94 GHz), wideband (1GHz instantaneous bandwidth) pulsed spectrometer with very high concentration sensitivity and low deadtime. In direct comparisons for PELDOR measurements with a Bruker X-band system using a MD4 cavity, using similar sample volumes, the S/N improvement is typically in the range 20-30, with modulation depths 2/3 that of X-band. Higher sensitivities have been noted for certain samples and sample-holder configurations. This sensitivity is achieved by using a non-resonant, high volume design. It is often assumed that large increases in concentration sensitivity are not possible at high fields because of the well known expected w0

1/2 scaling factor expected when scaling the same type of resonant cavity. However, that scaling law does not apply in this case. Such large increases in concentration sensitivity over large bandwidths at high fields (where the g-factor is resolved in nitroxides) are particularly useful for PELDOR measurements for: measuring samples at low concentration levels (reducing aggregation effects, instantaneous diffusion effects and inter-molecular effects), increasing time windows (measuring longer distances), and benefiting from increased signal to noise (reduced averaging times and accurate characterisation of spin label distance and angle distributions). The poster will give examples illustrating some of these advantages and point to ways where sensitivity can be further improved.

P32 Accurate Experimental Characterisa5on of Spin Label Distribu5ons in Symmetric Mul5-‐Spin Systems – using the MscS channel protein as an exemplar

Johannes McKay1, Richard Ward2, Christos Pliotas2, Hassane El Mkami1, Rob Hunter1, David Bolton1, Paul Cruickshank1, David Norman5, Bela Bode3, Olav Schiemann3, Jim Naismith2, Graham Smith1 1School of Physics and Astronomy, University of St Andrews, Scotland 2School of Biomolecular Sciences, University of St Andrews, Scotland 3School of Chemistry, University of St Andrews, Scotland 4School of Chemistry, University of Bonn, Germany 5School of Life Sciences, University of Dundee, Scotland It is well known that the conformational distribution of spin labels can significantly effect the observed mean and distance distribution seen by PELDOR measurements on protein systems that have been site-directed spin labelled. This is normally allowed for by computationally modelling the distribution of spin labels using such freely available programs such as MMM and MtsslWizard. However, these are not always fully accurate and they require a detailed model of the protein system. In this poster we describe an experimental technique and methodological approach for characterising the angular and distance distribution of a set of partially constrained spin labels in a symmetric oligomeric system. A set of orientationally selective PELDOR measurements are measured and computationally analysed in a way that allows the correlation between distance and angle distribution to be taken into account. The methodology automatically allows more precise measurements of distances within the protein, and potentially allows small angular conformational changes to be characterised. We also present evidence to suggest that it may be possible to determine the symmetry of an oligomeric structure, just from orientational PELDOR measurements. We demonstrate the technique using experimental PELDOR data from the heptameric MscS channel protein using the high sensitivity, high power W-band spectrometer HIPER, and comment on its applicability to other systems.

University of Dundee 6-10 April 2014 - RSC ESR Spectroscopy...

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