title: Active site structure and dynamics of cytochrome c3 from Desulfovibrio gigas immobilized on electrodes.
abstract: Cytochrome c3 from Desulfovibrio gigas is electrostatically adsorbed on Ag electrodes coated with self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid. The redox equilibria and electron transfer dynamics of the adsorbed four-heme protein are studied by surface enhanced resonance Raman spectroscopy. Immobilization on the coated electrodes does not cause any structural changes in the redox sites. The potential-dependent stationary experiments distinguish the redox potential of heme IV (-0.19 V versus normal hydrogen electrode) from those of the other hemes for which an average value of -0.3 V is determined. Taking into account the interfacial potential drops, these values are in good agreement with the redox potentials of the protein in solution. The heterogenous electron transfer between the electrode and heme IV of the adsorbed cytochrome c3 is analyzed on the basis of time-resolved experiments, leading to a formal electron transfer rate constant of 15 s(-1), which is a factor of 3 smaller than that of the monoheme protein cytochrome c.
authors.affiliation: Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Avenida da República Apt. 127, P-2780 Oeiras, Portugal.
authors.forename: A Jalila
authors.initials: AJ
authors.lastname: Simaan
authors.forename: Daniel H
authors.initials: DH
authors.lastname: Murgida
authors.forename: Peter
authors.initials: P
authors.lastname: Hildebrandt
mesh_terms: D001665:Binding Sites; D003574:Cytochrome c Group / Q000737:chemistry*; D003901:Desulfovibrio / Q000737:chemistry*; D004566:Electrodes; D004579:Electron Transport; D006418:Heme / Q000737:chemistry; D007700:Kinetics; D010084:Oxidation-Reduction; D011485:Protein Binding; D013059:Spectrum Analysis, Raman / Q000379:methods; D013997:Time Factors
chemical_list: D003574:Cytochrome c Group; D006418:Heme; C017165:cytochrome c(3)