Electrochemical studies of tau protein-iron interac4ons – poten4al … · 2017-12-14 ·...
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Suppor&ng Informa&on for Electrochemical studies of tau protein-iron interac4ons – poten4al implica4ons for Alzheimer's Disease. Soha Ahmadi 1,2 , Iraklii I. Ebralidze 1 , Zhe She 1 , Heinz-Bernhard Kraatz 1,2* 1. Department of Physical and Environmental Sciences, University of Toronto Scarborough, Canada 2. Department of Chemistry, University of Toronto, Canada 1 Procedure of gold electrode cleaning: 1. Chemical cleaning with piranha solu&on (H 2 SO 4 :H 2 O 2 3:1 v/v) for 1 min. 2. Polishing with alumina slurry (0.1 µm and 0.05 µm for 2 min each). 3. Sonica&on in deionized water and anhydrous ethanol for 10 min each. 4. Electrochemical cleaning u&lizing CV (100 scans) in 0.5 M KOH and 0.5 M H 2 SO 4 in the range of -2 to 0 and 0 to 1.5 volt respec&vely. Electrodes were rinsed with deionized water aTer each step and were blown dried with compressed N 2 aTer final step.
Transcript of Electrochemical studies of tau protein-iron interac4ons – poten4al … · 2017-12-14 ·...
Suppor&ngInforma&onfor
Electrochemicalstudiesoftauprotein-ironinterac4ons–poten4alimplica4onsforAlzheimer'sDisease.SohaAhmadi1,2,IrakliiI.Ebralidze1,ZheShe1,Heinz-BernhardKraatz1,2*1.DepartmentofPhysicalandEnvironmentalSciences,UniversityofTorontoScarborough,Canada2.DepartmentofChemistry,UniversityofToronto,Canada
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Procedureofgoldelectrodecleaning:
1.Chemicalcleaningwithpiranhasolu&on(H2SO4:H2O23:1v/v)for1min.2.Polishingwith
aluminaslurry(0.1µmand0.05µmfor2mineach).3.Sonica&onindeionizedwaterand
anhydrousethanolfor10mineach.4.Electrochemicalcleaningu&lizingCV(100scans)in0.5
MKOHand0.5MH2SO4intherangeof-2to0and0to1.5voltrespec&vely.Electrodes
wererinsedwithdeionizedwateraTereachstepandwereblowndriedwithcompressedN2
aTerfinalstep.
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0
10
20
30
40
50
60
0 0.1 0.2 0.3 0.4 0.5 0.6
j/µAcm
-2
Evs.(Ag/AgCl)/V
FigureS1.characteriza&onofmodifiedgoldsurfaceforstudythetau-ironinterac&onusing
differen&alpulsevoltammetry(DPV).Differen&alPulsevoltammogramsofgoldin10mM
[Fe(CN)6]3-/4-redoxprobeforsurfacecharacteriza&on.BareAuelectrode(orange),aTer
modifica&onwithLip-NHS(blue),followingimmobiliza&onofTau-410(green),andaTer
blockingwithethanolamineandback-fillingwithhexanethiol(purple).
Rs(Ωcm-2) CPE(fs-0.5cm-2) n RcT(Ωcm-2) W(fs-0.5cm-2)
Au-Lip-NHS 31.4±0.4 (5.2±0.5)x10-7 0.96±0.01 1167±148 (2.2±0.2)x10-4
Au-Lip-NHS-Tau 24.5±0.3 (11.9± 0.5)x10-7 0.91±0.01 2814±223 (4.5±0.8)x10-4
Modifiedgoldelectrode(MGE) 26.6±0.3 (9.4±0.8)x10-7 0.91±0.01 11300±1028 (2.2±0.9)x10-4
MGE-Fe(II) 28.8±0.4 (8.2±0.7)x10-7 0.91±0.01 4837±338 (3.5±0.9)x10-4
MGE-Fe(III) 26.6±0.4 (8.8±0.8)x10-7 0.92±0.01 8185±686 (1.4±0.3)x10-4
Table S1. Values of the equivalent circuit elements shown in Figure 1B and 2B for gold
surfacemodifica&onandtau-ironinterac&on.
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FigureS2.Δfvs.&meplotofQCMexperimentforimmobiliza&onofn-tauongold
surfacethroughLip-NHS.
Themassofn-tauonthegoldsurfacewascalculatedaTer4hoursusing
Sauerbreyequa&on:
Δf=-Cf.Δm
Δf=-256Hz
Cf=1.34ng/Hz
Theimmobilizedn-tauongoldsurfacewas975ngcm-2,whichisequalto14x1012
moleculespercm2ofgoldsurface.Byassumingthattaumoleculehasaspherical
shapethemaximumnumberoftaumoleculeforamonolayerfilmonthegold
surfacewillbe51x1012moleculespercm2.Thetheore&calnumberisalmost4
&mesmorethanthenumberoftaumoleculesfindingfromQCMexperiment,
whichconfirmtheforma&onofmonolayertaufilm.
Δf/H
z -256 Hz
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R²=0.99652
R²=0.99523
R²=0.99894
R²=0.99849
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-4
0
4
8
0.5 1.5 2.5 3.5
j/µA
cm
-2
Squarerootofscanrate(v/s)1/2
FigureS3.InfluenceofthescanrateontheCVelectrochemicalresponseof10mM[Fe(CN)6]3-/4-formodifiedgoldelectrodesaTerincuba&nginFe(II)(square)andFe(III)(dots)solu&ons.Plotofpeakcurrentdensityvsthesquarerootofthescanrateoftheoxida&onandreduc&onof[Fe(CN)6]3-/4-
FigureS4.Cyclicvoltammogramsofgoldelectrodesin10mMRu(NH3)6Cl3redoxprobeforstudytheiron/tauinterac&onbyusingathree-electrodesetupwithagolddisc,aPtwireandAg/AgClelectrodeasworkingelectrode,auxiliaryelectrodeandreferenceelectrode,respec&vely.Baregold(blueline),modifiedgoldelectrode(solidblack)andaTerincuba&ngin1mMFe(III)(greenline)and1mMFe(II)(redline).
-0.5
-0.3
-0.1
0.1
0.3
-0.4 -0.3 -0.2 -0.1 0 0.1
j/m
Acm
-2
E/V(vsAg/AgCl)
FigureS6.Plotofthecurrentdensi&esofn-taufilmongoldelectrodeinthepresenceofFe(II)solu&onatdifferentpH.(Ag/AgClasareferenceelectrodeandPtwireasacounter-electrode)Errorbarsshowthestandarddevia&onoftriplicatemeasurements.Currentdensi&esweretakenfromdifferen&alpulsevoltammograms(DPV)in10mM[Fe(CN)6]3-/4-redoxprobe.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
5.4 6.4 7.4 8.4
j/µAcm
-2
pH
5.4 6.4 7.4 8.4
A
B
FigureS5.Scanningtunnelingmicroscopy(STM)imageoftau-modifiedgold
surfaceaTerincuba&nginFe(II)(A)andFe(III)(B)solu&on.
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290 285 280
M+F e2M+F e+T
B inding E nerg y,eV
290 285 280
M+T +TAu+L +T +A
B inding E nerg y,eV
A B
C D
FigureS7.Representa&veXPSdatafortau-modifiedgoldsurfaces.(A)TheC(1s)
spectrafortau-modifiedgoldelectrodeaTerincuba&nginFe(II)(dashedred)and
aTersecondincuba&onintausolu&on(solidblack).(B)TheC(1s)spectrafortau-
modifiedgoldelectrodeaTerincuba&nginFe(III)(dashedred)andaTersecond
incuba&onintausolu&on(solidblack).(C)Au4f5/2andAu4f7/2forbaregold(solid
black),modifiedgoldelectrodewithtau(solidred)andaTerre-incuba&onintau
solu&on(solidblue).(D)Au4f5/2andAu4f7/2fortau-modifiedgoldelectrode
aTerincuba&onintausolu&oninabsenceofiron(solidblue),inpresenceofFe(III)
(solidred)andFe(II)(solidgreen).
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FigureS8.UV-VisspectrumofFe(ClO4)3andFe(ClO4)2indeionizedwaterandTrisbuffer(pH
7.4)withthescanrateof600nm/minanddataintervalof1nm.(A)TheFe(ClO4)3in
deionizedwater(greenline),Fe(ClO4)3inTrisbuffer,pH7.4(blueline),Fe(ClO4)2indeionized
water(purpleline)andFe(ClO4)2inTrisbuffer,pH7.4(redline).(B)Time-dependent
experimentinTrisbuffer(pH7.4):FreshFe(ClO4)3(greenline),Fe(ClO4)3solu&onaTerone
hour(purpleline),freshFe(ClO4)2solu&on(blueline),Fe(ClO4)2solu&onaTeronehour
(redline).
0
0.4
0.8
1.2
1.6
190 290 390 490 590 690 790
Absorban
ce
Wavelenght/nm
A
0
0.4
0.8
1.2
1.6
190 290 390 490 590 690 790
Absorban
ce
Wavelenght/nm
B
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-2
-1
0
1
2
-0.1 0.1 0.3 0.5 0.7
j/mAcm
-2
Evs.(Ag/AgCl)/V
FigureS9.Cyclicvoltammogramsofgoldelectrodesin10mM[Fe(CN)6]3-/4-redoxprobeforcontrolexperimentoftauphosphoryla&onusingathree-electrodesetupwithagolddisc,aPtwireandAg/AgClelectrodeasworkingelectrode,auxiliaryelectrodeandreferenceelectrode,respec&vely.(A)Modifiedgoldelectrodewithn-tau(redline),modifiedgoldelectrodeaTerincuba&nginGsk-3βwithATP(greenline)andGsk-3βwithoutATP(blackline).(B)Modifiedgoldelectrodeelectrodewithn-tau(redline),modifiedgoldelectrodeaTerincuba&nginSrcwithATP(greenline)andSrcwithoutATP(blackline).
-2
-1
0
1
2
-0.1 0.1 0.3 0.5 0.7
j/mAcm
-2
Evs.(Ag/AgCl)/V
B
A
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0
10
20
30
40
0 1000 2000 3000 4000 5000 6000 7000 8000
Δf/Hz
Time/s
FigureS10.Δfvs&meplotofQCMexperimentforthephosphoryla&oncontrol
experiment.Goldmodifiedsurfacewithn-tauincubatedinGSK-3β(A)andSrc(B)
inappropriatebufferinabsenceofATPfor2hoursΔfislessthan20Hzforboth
GSK3βandSrc,sugges&ngthatthenon-specificadsorp&onisnegligible.
0
10
20
30
40
0 2000 4000 6000 8000
Δf/Hz
Time/s
B
A
