Electrochemistry of cytochrome c3 at a lipid-modified graphite electrode

Abstract

The electron transfer reactions between a lipid-modified, pyrolytic graphite (PG) electrode and tetraheme cytochromes c 3 have been studied at different ionic strengths by cyclic and square-wave voltammetry. In 0.1 M phosphate buffer (pH 7.6), no signal was detected at the PG electrode coated with a mixed layer of phosphatidylcholine (PC) and cholesterol (CH) (containing 5 mg ml −1 PC). The signals corresponding 1to the reduction-re-oxidation of cytochrome c 3 from Desulfovibrio vulgaris Hildenborough (DvH) were restored by doping the lipid layer with laurate anions. At low ionic strengths (10 mM phosphate), using the same (PC-CH + LA)-modified PG electrode, DvH cytochrome c 3 molecules are incorporated into the lipid layer. The stability of the film has been studied after transfer into an electrolyte solution. No incorporation was observed in the case of cytochrome c 3 from Desulfovibrio desulfuricans Norway. The results support the electrostatic nature of the interactions between cytochrome c 3 and the lipid layer. This approach to the electrochemistry of cytochrome c 3 opens new ways for the study of protein | lipid interfaces.