Figure 1.

(Top panel) Electrochemical oxidation of Pol2_COREexo^– using DNA-modified electrodes. DNA substrate is attached to gold (Au) surface through a 5′ alkanethiol group. Complementary matched DNA strand is slightly longer, yielding a 7-nt overhang that serves as the natural binding substrate for Pol2_COREexo^–. (Bottom panel) CV scans of electrochemically oxidized Pol2_COREexo^– (5 μM) exhibit a large cathodic CV signal centered around −140 V vs NHE (green trace), but no signal is observed when Pol2_COREexo^–CysX_MUT (red trace) or buffer (5 mM NaH₂PO₄, 50 mM NaCl, pH 7.0; black trace) is electrochemically oxidized. Potential applied (E_appl) for bulk oxidation is 412 mV vs NHE for 500 s. CV scan rate = 100 mV s^–1. Pol2_COREexo^– protein sample concentrations used for cyclic voltammetry experiments are 5 μM (ε[4Fe4S]₄₁₀ = 17 000 M^–1 cm^–1).