21.

(a) Structure of W-dependent NvFdhAB (PDB: 6SDV) adsorbed onto an electrode, highlighting the reversible electron transfer to and from the W-active site through the [Fe–S] clusters. (b) Cyclic voltammograms of ideal irreversible and reversible electrochemical reactions. Numerical data adapted from ref with permission from National Academy of Sciences, copyright 2011. (c) Protein film voltammetry of Fdh from S. fumaroxidans adsorbed onto polished pyrolytic graphite edge electrode in 10 mM CO₂ and 10 mM sodium formate (pH 6.4) showcasing the interconversion of CO₂ and formate at the reduction potential (black dashed line). The background current is represented by the dashed line. The conditions employed were 100 mV s^–1 scan rate, 37 °C and 1000 rpm electrode rotation. Numerical data adapted from ref with permission. Copyright 2008 National Academy of Sciences.