The Direct Electron Transfer Reactions of Cytochromecat Electrode Surfaces

Abstract Examples of facile electron transfer between electrode surfaces and electron transfer proteins were first reported nearly twenty years ago. Substantial progress has been achieved in understanding the fundamental requirements that must be met in order to observe such reactions. Despite the large body of work that has now been published on a host of examples of such reactions, there continues to be a lack of understanding over just what conditions must be met in order to use direct electrochemical methods to characterize the electron transfer thermodynamics and kinetics of electron transfer proteins. Part of the problem lies in the inherent difficulties associated with using solid electrodes. Equally as important is the wide range of attention that has been paid to the purity of the electron transfer protein solutions being studied. The goal here is to bring together those aspects of this problem that enjoy some degree of agreement among scientists in this field and to reflect upon those issues that remain to be resolved. The widely studied electron transfer protein, cytochrome c, will be the forcus of this paper.