ABSTRACT
The biological role of copper ions is in mediation and catalysis of redox reactions. The reactivity of the different copper sites present in blue copper oxidases is naturally determined by their different functional roles. This chapter focuses primarily on the aspects of the mechanism of electron transfer of single copper proteins which can be interpreted in terms of presently available structural information. Quantum mechanical tunneling has also been invoked to explain biochemical electron-transfer processes. A critical factor in biological electron-transfer mechanisms is the necessity of the reacting molecules to attain the proper relative orientation before electron transfer. A comparison of the reaction parameters determined for protein-small molecule electron-transfer with those for protein-protein electron-transfer makes the differences obvious. At least with hydrophilic reagents the former reactions are generally characterized by very small activation enthalpies so that the rates are essentially determined by the very large negative activation entropies.
