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![Page 1: Christopher Leavitt Yale University Vibrational spectra of cryogenic peptide ions using H 2 predissociation spectroscopy.](https://reader033.fdocuments.us/reader033/viewer/2022050909/56649f1d5503460f94c34e31/html5/thumbnails/1.jpg)
Christopher LeavittYale University
Vibrational spectra of cryogenic peptide ions using H2 predissociation spectroscopy
![Page 2: Christopher Leavitt Yale University Vibrational spectra of cryogenic peptide ions using H 2 predissociation spectroscopy.](https://reader033.fdocuments.us/reader033/viewer/2022050909/56649f1d5503460f94c34e31/html5/thumbnails/2.jpg)
Motivation
• Characterize the effects of protonation in peptide ions
• Investigate the dependence of varying substituents across the peptide backbone to peptide conformation
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Structural Probe: Methylation
+
H2O
N
H
O
NHH
O
OH
O
O
NHH
HN
O
OHH
H
N
H
O
N+HH
O
OH
H
H+
N
CH3
O
N+HH
O
OH
H
R= H, CH3
N
R
O
N+RH
O
OH
H
N
H
O
N+HH
O
OH
H
N
H
O
N+H3C
H
O
OH
H
N
CH3
O
N+H3C
H
O
OH
H
![Page 4: Christopher Leavitt Yale University Vibrational spectra of cryogenic peptide ions using H 2 predissociation spectroscopy.](https://reader033.fdocuments.us/reader033/viewer/2022050909/56649f1d5503460f94c34e31/html5/thumbnails/4.jpg)
Cryogenic Mass Spectrometry: H2-Tagging in a Quadrupole Ion Trap
Wiley-McLarenextraction region
Ion optics
To time-of-flightand 2-D infrared analysis
Electrosprayneedle
Heated capillary
90° ionbender
RF only quadrupolesH2/He filled 3-D quadrupoleion trap with temperature
control to 10 KEinzel
Octopoles
1st skimmer
2nd skimmerDifferential
aperture
50 K heat shield
1x10-5 1.5x10-23x10-7Pressure (Torr) 1.5 760
GlyGlyH+
T = 300K
T = 10K
Ion
Inte
nsity
(A
.U.)
Mass (m/z)
+H3N
O
HN
O
OH
1 2 3 4 5 6
* *
*
* * * * *133 137 141 145
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FromESI
600-4500 cm-1
2m Flight TubeMCP Detector
Mass Gate
Reflectron
Yale Photofragmentation TOF Spectrometer
Ion Optics
A+ · (H2)m + h → A+ · (H2)n + (m-n) H2
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D0
Infrared Spectrum of GlyGlyH+
800 1200 1600 2800 3200 3600 4000
Photon Energy, cm-1
Pre
dis
so
cia
tio
n Y
ield
H2 stretch
Polfer, N. C., Oomens, J. Mass Spectrom. Rev. 2009, 28, 468-494Wu, R., McMahon, T. B. J. Phys. Chem. B 2009, 113, 8767-8775Kamrath, M., et. al. J. Am. Chem. Soc. 2011, 133, 6440-6448
IVR
IRMPD•Room Temperature•Tens to hundreds of photons are necessary to dissociation molecules
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Infrared Spectrum of GlyGlyH+
800 1200 1600 2800 3200 3600 4000
Photon Energy, cm-1
Pre
dis
so
cia
tio
n Y
ield
H2 stretch
Wu, R., McMahon, T. B. J. Phys. Chem. B 2009, 113, 8767-8775Kamrath, M., et. al. J. Am. Chem. Soc. 2011, 133, 6440-6448
IVR
Cryogenic H2 Predissociation•Ions are vibrationally cold•Single photon results in dissociation
H2
H2
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MP2/6-311++G(d,p)
800 1200 1600 2800 3200 3600 4000
Photon Energy, cm-1
Ca
lcu
late
d I
nte
ns
ity
Pre
dis
so
cia
tio
n Y
ield
H2 stretch
O-H stretch
Protonated Amine
freeH2
N-H Region
Amide Region
Fingerprint Region
Wu, R., McMahon, T. B. J. Phys. Chem. B 2009, 113, 8767-8775Kamrath, M., et. al. J. Am. Chem. Soc. 2011, 133, 6440-6448
Infrared Spectrum of GlyGlyH+
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n = 1
Pre
dis
soci
atio
n Y
ield
3100 3200 3300 3400 3500 3600 3700
Photon Energy, cm-1
n = 2
Cal
cu
late
d I
nte
nsi
ty
n = 0
O-H stretch
H2 solvation of GlyGlyH+
Asym. NH2
stretch
Amide NH
Sym. NH2
stretch
O-Hstretch
Asym. NH2
stretch
Amide NH stretch
Sym. NH2
stretch
Optimization and Frequency Calculations at MP2/6-311+G(d,p)
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Structural Probe: Methylation
1.065
1.689
127.2°
GlyGlyH+(1)
1.069
128.0°
1.654
GlySarH+(1)
1.8401.043
118.0°
SarSarH+(1)SarGlyH+(1)
1.9551.038
114.0°
a) b)
c) d)
Optimization and Frequency Calculations at MP2/6-311+G(d,p)
Extended,“all trans” Kinked,
carboxyl rotated
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2400 2600 2800 3000 3200 3400 3600 3800 4000 4200
Photon Energy, cm-1
freeH2
freeD2
Pre
diss
ocia
tion
Yie
ld
O-H stretch
Asym. NH2
Amide NH
Sym. NH2
Amine NH
GlyGlyH+•(H2)1
SarSarH+•(D2)2
SarGlyH+•(H2)2
GlySarH+•(D2)2
*
*
N-H Stretching Region: Methylation Study
N
CH3
O
N+HH
O
OH
H
N
H
O
N+HH
O
OH
H
N
H
O
N+H3C
H
O
OH
H
N
CH3
O
N+H3C
H
O
OH
H
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Fingerprint Region: Methylation Study
800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900
Photon Energy, cm-1
Pre
diss
ocia
tion
Yie
ld
CO-HBend
Amide II C=O
Amide I
*
*
Optimization and Frequency Calculations at MP2/6-311+G(d,p)
CO-H Bend
Amide II
Amide I
C=O
N
CH3
O
N+HH
O
OH
H
N
H
O
N+HH
O
OH
H
N
H
O
N+H3C
H
O
OH
H
N
CH3
O
N+H3C
H
O
OH
H
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Missing Shared Proton Bands
MP2/6-311++G(d,p)
800 1200 1600 2800 3200 3600 4000
Photon Energy, cm-1
Ca
lcu
late
d I
nte
ns
ity
Pre
dis
so
cia
tio
n Y
ield
H2 stretch
O-H stretch
Protonated Amine
freeH2
N-H Region
Amide Region
Fingerprint Region
Wu, R., McMahon, T. B. J. Phys. Chem. B 2009, 113, 8767-8775Kamrath, M., et. al. J. Am. Chem. Soc. 2011, 133, 6440-6448
![Page 14: Christopher Leavitt Yale University Vibrational spectra of cryogenic peptide ions using H 2 predissociation spectroscopy.](https://reader033.fdocuments.us/reader033/viewer/2022050909/56649f1d5503460f94c34e31/html5/thumbnails/14.jpg)
0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2
0
2500
5000
7500
10000
N-H Distance, Å
En
erg
y, c
m-1
GlyGlyH+
GlySarH+
SarGlyH+
SarSarH+
H2N
CH2
C
OH
Identifying the Shared Proton Mode
0
1
1555 cm-1
Optimization calculations at MP2/6-311++G(d,p)
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Identifying the Shared Proton Mode
800 1000 1200 1400 1600 1800 2000
Pre
diss
ocia
tion
Yie
ld
Photon Energy, cm-1
N
H
O
NHH
O
OH
Na+
N
H
O
N+HH
O
OH
H
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800 1200 1600 2400 2800 3200 3600
Photon Energy, cm-1
Identifying the Shared Proton Mode
•All structures are nominally protonated on the amino group, and feature an intramolecular H-bond between the amino group and the amide oxygen.
•Addition of a methyl group at the amide position induces rotation of the peptide backbone.
•Isotope substitution to help confirm the assignment of the intramolecular h-bond
•Isomer selective IR-IR double resonance experiments to determine the extent of multiple isomers present.
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Thanks to:Mark JohnsonMike KamrathArron WolkEtienne GarandPeter JordanRachael RelphHelen GerardiKrissy BreenAndrew DeBlaseJoe FournierGary WeddleTim Guasco(UCSD)Mike Van Stipdonk (Wichita State)Anne McCoy(The Ohio State University)
Acknowledgements
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hprobe
Reflectron
Sig
nal
Time of Flight, ms
prob
e fr
agm
ent
pum
p fr
agm
ent
Detector
Predissociation Dip Spectroscopy
hpump
(scanned)
Coaxial TOF
±1.5 keV
(fixed)
Our Challenge:
Not enoughtemporal separation!
The Solution:
Earlier firstlaser crossingand mass selection!