Membrane electrodes can modulate the electrochemical response of redox proteins — direct electrochemistry of cytochrome c

Membrane (carbon or gold) electrodes constructed from dialysis membranes varying in cutoff and charge are used to investigate the electrochemical behavior of c-type cytochromes, especially cytochrome c. It is shown from cyclic voltammetry experiments that cytochrome c exhibits direct electrochemical responses at negatively charged membrane (graphite-, glassy carbon-, mercury film glassy carbon-, and gold) electrodes. Different factors (pre-treatment of the membrane, effect of positively charged species, ionic strength, pH, effect of the entrapped layer thickness) have been examined. The electrochemical response of multiheme cytochromes c3 at the membrane electrode is also investigated. It is demonstrated that the electrochemistry of cytochrome c at the membrane electrodes is essentially governed by favorable electrostatic interactions, and that other factors (especially adsorption and the presence of denatured forms) do not play a dominant role. A discussion on the electrochemistry of c-type cytochromes is given.