Electrochemical Behavior and Nitric Oxide Interaction of Immobilized Cytochrome c′ fromRhodocyclus gelatinosus

Cytochrome c′ from Rhodocyclus gelatinosus was immobilized at a mercaptosuccinic acid modified gold electrode for the first time and the electrochemical behavior was characterized. The conditions of protein adsorption were investigated. Buffer and pH variations indicated a mainly nonionic nature of interaction. The heterogeneous electron transfer rate constant of the immobilized protein was determined (ks=30 s –1). The adsorption was found to be stable in protein-free solution for about one week. The immobilized cytochrome c′ was accessible for nitric oxide molecules in solution. The interaction resulted in an enhanced reduction current in the cyclic voltammogram. When polarized at –220 mV (vs. Ag/AgCl) the electrode current showed a linear dependence upon NO concentration. The signal was proven to be sensitive within the nanomolar range.