Reversible Oxidation of Spinach Ferredoxin at Surface-Modified Electrodes

The oxidation of Spinacia oleracea ferredoxin [2Fe-2S] at modified and unmodified gold and indium tin oxide electrodes was studied by cyclic voltammetry. The results are compared to previous reports and, in some cases, with the results of quantum chemical simulations. We found that protonated 4-mercaptopyridine attached to a gold surface by self-assembly stimulated the oxidation of ferredoxin at acidic pH values but not in a neutral solution. Furthermore, we found that a gold electrode with a poly-l-lysine film attached to a self-assembled monolayer of mercaptoundecanoic acid elicited a reversible oxidation-reduction pair at neutral pH with a midpoint potential near the reported formal potential of spinach ferredoxin. This work compares and discusses the oxidation of ferredoxin by a range of electrode materials. (C) 2008 The Electrochemical Society.