SUPPORTING INFORMATION
Electrochemistry of the [4Fe4S] cluster in base exc
ision repair proteins:
Tuning the redox potential with DNA
Phillip L. Bartels,
†
Andy Zhou,
†
Anna R. Arnold,
†ᴈ
Nicole N. Nuñez,
‡
Frank N. Crespilho,
§
Sheila S. David,
‡
Jacqueline K. Barton
†
*
Figure S1.
CV scans of storage buffer, a CNT/Nafion thin film
, and a WT EndoIII/CNT/Nafion
thin film. CNTs increase the capacitance dramatical
ly relative to buffer alone (20 mM sodium
phosphate, pH 7.5, 150 mM NaCl, 0.5 mM EDTA; green
plot), although they also enhanced the
signal due to charged surface species (around 200 m
V vs NHE) in addition to a signal near -80 mV
vs NHE attributable to oxides on the CNTs themselve
s (brown plot). Notably, neither of these
peaks exhibited any splitting, indicative of rapid
processes taking place at the surface.
Incorporation of 75
μ
M EndoIII into the thin film suppressed both of the
se signals, and resulted in
the appearance of a reversible signal with noticeab
le peak splitting near 100 mV vs NHE. The
much higher capacitance in these CVs relative to th
ose in Figure 1 is due to the addition of 3-6
more layers of CNT/protein than later CVs, which ma
de the comparison easier but also caused
the EndoIII peaks to be less clearly defined. All C
Vs were taken at a scan rate of 100 mV/s.
Figure S2.
Scan rate dependence of the current for EndoIII an
d MutY, and peak splitting for WT
EndoIII. The linear dependence of current on scan r
ate confirms that the protein is adsorbed to
the electrode surface (EndoIII, top right; MutY, to
p left). Because the proteins were adsorbed to
the surface, Laviron’s method for non-diffusive syst
ems was applied to estimate electron transfer
rates (k
ET
) and coefficients (α) for EndoIII (bottom; the sma
ll size of the MutY signal precluded
Laviron analysis).
Figure S3.
Electrochemistry controls on the PGE electrode. To
determine the electroactive area of
the PGE electrode and to verify the accuracy of mea
sured potentials, 2 mM [Ru(NH
3
)
6
]
3+
in
EndoIII storage buffer was added in the presence (d
ark green) and absence of CNTs (light green).
Notably, while the peak splitting decreased slightl
y in the presence of CNTs, the midpoint
potential was unaltered.