Cytochrome c electrochemistry on peptide self-assembled monolayers

A short chain peptide is covalently attached to an evaporated gold electrode to form a biocompatible self-assembled monolayer (SAM) surface. The peptide is designed to optimize the interfacial interaction of horse heart cytochrome c (cytc) through the electrostatic interaction of the carboxylate group on the terminal amino acid glutamate and the amine on lysine in cytc. Cytc exhibits quasi-reversible voltammetry and is stable on the time scale of the experiments. Marcus theory is used to calculate the electron transfer rates, which are ~5 times faster for cytc/peptide/Au compared to cytc/11-mercaptoundecanoic acid/Au SAMs of similar chain length. The formal potentials also shift for the cytc/peptide system ~20 mV more positive than cytc adsorbed to 11-mercaptoundecanoic acid-SAM/Au electrodes.