Electronic structure contributions to electron transfer in blue Cu and Cu-A

The experimentally determined electronic structures of mononuclear blue Cu and binuclear Cu-A centers are summarized and their relation to intra-and i nter-protein electron transfer (ET) kinetics are described. Specific contri butions of the electronic structures of these two broad classes of Cu ET pr oteins to H-AB, lambda, and Delta E degrees are discussed. Also, the role o f the protein structure in determining key geometric features which define the electronic structures of the metal sites in these proteins is considere d.