Electron Transfer of Cytochrome c on Surface-Enhanced Raman Scattering-Active Substrates: Material Dependence and Biocompatibility.

Surface-enhanced Raman spectroscopy (SERS) represents a powerful approach for studying the structure and reaction of proteins in fundamental and applied sciences. The surface properties of SERS-active materials determine important parameters such as Raman enhancement ability, biocompatibility, and electronic communication between supports and proteins. Here, electron transfer (ET) of Cyt c on noble metals and transition metals is investigated by SERS spectroscopy. The results here indicate that the ET occurs from the reduced state of Cyt c to silver substrate, depending on the laser wavelengths. Nickel and cobalt can directly transfer electrons to the oxidized state of Cyt c, which enables a reductive activity of these transition metal nanoparticles (NPs). This study demonstrates the role of transition metals as electron donors for Cyt c and has proved that the charge transfer theory for SERS is applicable for explanation of the ET between Cyt c and Ag NPs.