SUPPLEMENTARY INFORMATION Direct electron transfer to a metalloenzyme redox center coordinated to a monolayer protected cluster.
Jose M. Abad,†* Mhairi Gass, ‡ Andrew Bleloch,‡ and David J. Schiffrin.† Chemistry Department, University of Liverpool, Liverpool L69 7ZD United Kingdom UK SuperSTEM, Daresbury Laboratory, Daresbury, Cheshire WA4 4AD, United Kingdom *e-mail:
[email protected] †
‡
70
Frequency (% )
60 50 40 30 20 10 0 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4
Particle diameter (nm)
10 nm
5 nm
Figure S1. HAADF-STEM images of thioctic acid-protected gold clusters (TAAuMPCs). The intensity of the images is proportional to the number of gold atoms present in the clusters. S1
Absorbance
1.5
1.0
0.5
0.0 200
300
400
500
600
700
800
900
W avelength (nm )
Figure S2. UV-visible spectrum of thioctic acid-protected gold clusters (TAAuMPCs) in water at pH 7.5.
Current ( µ A)
30 0 -30 -60 -90
HS
SH
HS
SH
HS
SH
-120 -1.4
-1.2
-1.0
-0.8
-0.6
-0.4
-0.2
Potential (V vs. SCE) Figure S3. Cyclic voltammogram in 0.5 M KOH of a gold electrode modified with a SAM of biphenyl-4,4'-dithiol. Scan rate 100 mV/s; nitrogen saturated.
S2
+e-
Cu2+- Tyr·
-e-
(GOaseox)
Cu2+- Tyr (GOasesemi)
ο
E` (mV vs. SCE)
350 300 250 200 150 100 50
5
6
7
8
9
10
pH
Figure S4. Variation of the formal potential on pH for the reduction of the Cu(II)tyroxyl radical.
S3
0.6
A
4
0.4
B
2
0.2
0
-0.2
-2
-0.4
-4
Current (µA)
Current (µA)
0.0
0.2 0.1 0.0
1.5 1.0 0.5 0.0 -0.5
-0.1
-1.0 -0.2 -0.4
-0.2
0.0
0.2
Potential (V vs. SCE)
0.4
-1.5 -0.4
-0.2
0.0
0.2
0.4
Potential (V vs. SCE)
Figure S5. Cyclic voltammograms at 5 mV/s (A) and 100 mV/s (B) scan rates on a gold electrode modified with a SAM consisting of biphenyl-4,4'-dithiol and carboxylate-gold nanoparticles before (background, black line) and after incubation GOase protein solution (red line). (Bottom) The cyclic voltammograms shown have been background corrected. Measurements were carried out in nitrogen saturated 20 mM MES buffer pH 7.5.
S4
6
Ipc(µA)
4
2
0 0.0
0.1
0.2
0.3
0.4
0.5
0.6
-1
Scan rate (V s ) Figure S6. Plot of cathodic peak current vs. scan rate for the CuII-Tyr• (GOaseox) / CuII-Tyr¯ (GOasesemi) redox couple.
0.08
Epc (V vs. SCE)
A 0.06
0.04
0.02
0.00 -0.6
-0.4
-0.2
0.0
0.2
Log ν (V s-1) .
S5
Epa (V vs. SCE)
0.34
B
0.32
0.30
-0.8
-0.6
-0.4
-0.2
0.0
0.2
Log ν (V s-1) .
0.35
∆Ep (V vs. SCE)
C 0.30
0.25
0.20 -0.8
-0.6
-0.4
-0.2
0.0
0.2
Log ν (V s-1) .
Figure S7. (A) and (B) dependence of the anodic and cathodic peak potentials on the logarithm of the scan rate; (C) similar dependence for ∆Ep. The heterogeneous electron transfer rate constant (ksh) was calculated for ∆Ep>200/n mV using the Laviron’s equation31: log ksh = α log(1 − α ) + (1 − α ) log α − log( RT / nFv) − α (1 − α )nF∆E p / 2.3RT
S6
where α is the electron-transfer coefficient calculated the slopes (vc, va) of the plots (A,B) by using α/(1-α) = va/vc.,
10
m
-1
8 6 4 0.00
0.02
0.04
0.06
0.08
0.10
-1
Scan rate (V s ) Figure S8. Dependence of the m parameter of the Laviron method31 on scan rate for the calculation of the heterogeneous electron transfer rate constant (ksh) for ∆Ep
