ABSTRACT
Twenty-ve years ago, few people associated enzymes with dynamic (amperometric) electrochemistry in any context other than biosensor research. There has been a handful of articles describing catalytic turnover by enzymes (structurally ill dened at that time) adsorbed on electrodes; however, the results were not interpreted beyond comments that the enzyme established an electrode potential that was appropriate for the substrate redox couple being studied.1 Much more has been published about (noncatalytic) the electrochemistry of small electron carrier proteins in solution: the important breakthrough being the revelation, independently by the groups of Hill2 and Kuwana,3 that a solution of mitochondrial cytochrome c exhibits reversible cyclic voltammetry (CV) at certain electrodes. Cytochrome c is more than 60 times as massive as ferrocene yet the CV in each case was of textbook shape, with peak currents determined by the rate of diffusion of protein to the electrode surface. Given the three-dimensional (3D) structure of cytochrome c known at that time and our maturing understanding of long-range electron transfer, the results meant that there
6.1 Historic Context ............................................................................................205 6.2 Principles ......................................................................................................206
