Adsorption of cytochrome c on diamond

The adsorption and conformational state of the electron transfer protein cytochrome c (cyt c) on flat, boron doped polycrystalline diamond electrodes was investigated using electrochemicaltechniques and atomic force microscopy (AFM). An electrochemical reduction wave from the adsorbed protein was identified as oxygen reduction, which is catalysed by the deformed heme redox centre of cyt c. We show that this catalytic activity only occurs after partial denaturation of cyt c. Therefore the reduction peak was used for characterization of the conformational state of adsorbed cyt c. AFM characterizations with molecular resolution show different conformational states of cyt c on diamond surfaces ranging from native to denaturated. Both applied techniques indicate that hydrophobic hydrogenated diamond tends to denaturate cyt c upon adsorption, while wet chemically oxidized diamond surfaces can provide extensive but non-denaturating cyt c adsorption. The conformation and orientation of cyt c on wet chemically oxidized diamond is beneficial for the electron transfer between the protein redox centre and the diamond electrode even in the presence of oxygen.