Mitochondiral cytochrome c functions as an electron transfer agen both in vivo and in vitro, and reduces cytrochrome c oxidase in the terminal step of aerobic respiration. Extensive chemical modification of the E-amino groups of lysines, differential protection experiments, and site-directed mutagenesis studies have revealed that six or seven lysine residues surrounding the heme cervice of cyt c play an important role in binding interations and electron transger with most of its redox partneres. Intraprotein electronic coupling between these residues and the heme center is of interest in the context of the relative efficiencies of different through-bond electron-tunneling pathways. We are investigating these pathways using electrochemistry at chemically modified surfaces. Gold electrodes modified with functionalized alkane thiols provide complimentary surfaces for cytochrome c (HOOC-SAMs) and CuA, the soluable binding domain of cytochrome c oxidase (NH2-SAMs). Electrochemiacally triggered redox reactions through these SAMs yield ET data as a function of both driving force and distance; analysis of the data allows an estimate of the intramolecular coupling form the redox center to specific terminal lysine (cyt c) and or aspartate (CuA) residues on the surface.