Electrochemical Behavior of Ferredoxins Adsorbed on Mercury Electrode Surface. Cyclic d.c. and a.c. Voltammetric Studies with Hanging Mercury Drop Electrode

Abstract

Abstract The electrochemical behavior of Clostridium pasteurianum ferredoxin and spinach ferredoxin was studied by cyclic d.c. and cyclic phase-selective a.c. voltammetry with a hanging mercury drop electrode. An irreversible adsorption of these ferredoxins on the electrode surface is described. In successive cyclic voltage scans both d.c. and a.c. voltammograms of ferredoxins change gradually in both height and form until a steady state is attained, indicating that the ferredoxins adsorbed on the electrode surface decompose to cluster-free ferredoxins. Apoferredoxins give the same voltammograms as the steady state voltammograms of ferredoxins. The steady state voltammograms are assigned to RSH/RSHg redox reaction of the cysteine residues in apoferredoxin. At pH lower than 8 the d.c. waves are explained by an equation for reversible one-electron surface redox reaction. Kinetic parameters of the redox reaction were determined by a.c. voltammetry.