Electron transfer in SAM/cytochrome/polyelectrolyte hybrid systems on electrodes: a time-resolved surface-enhanced resonance Raman study.

Silver electrodes were covered with mixed self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) and 11-mercaptoundecanol (MU) and subsequently coated with alternating layers of cytochrome c (Cyt) and poly(anilinesulfonic acid) (PASA). The immobilized protein is electroactive and retains its native structure. Compared to the case of systems on gold electrodes, the stability of the assembly was found to be decreased.

On the electron transfer mechanism between cytochrome C and metal electrodes. Evidence for dynamic control at short distances.

Cytochrome c was coordinatively bound to self-assembled monolayers of pyridine-terminated alkanethiols on Au and Ag electrodes. The mechanism of heterogeneous electron transfer of the immobilized protein was investigated by cyclic voltammetry and time-resolved surface-enhanced resonance Raman spectroelectrochemistry. The temperature, distance, and overpotential dependencies of the electron transfer rates indicate a change of mechanism from a tunneling controlled reaction at long distances (thicker films) to a solvent/protein friction controlled reaction at smaller distances (thinner films).