Electrochemical, photoelectrochemical, electrocatalytic and catalytic reduction of redox proteins

Redox proteins catalyse 1 the reactions of a wide variety of otherwise intractable substrates, such as dinitrogen, alkalies, arenes, terpenes and steroids. Two major factors impede the utilization of these enzymes—the inefficient electron transfer between the enzyme and electrode, and the properties often, but not inevitably, associated with enzymes, such as instability, complexity, and expense. We have now shown that the former can be overcome and that proteins can be coupled, via electrodes, to a number of energy sources; the latter is 2 the subject of much effort elsewhere. We demonstrated previously 3–6 that certain redox proteins can be reduced very efficiently electrochemically (Fig. 1a). Light and hydrogen are the two other convenient energy sources that could be used for such reductions, and we now report the reduction of cytochrome c by these means.