ELECTROCHEMICAL INVESTIGATIONS OF THE STRUCTURE AND ELECTRON-TRANSFER PROPERTIES OF PHOSPHOLIPID-BILAYERS INCORPORATING UBIQUINONE

Bilayer assemblies consisting of octadecanethiol (OM) and L-alpha-dipalmitoyl phosphatidylcholine (DPPC) were formed at the gold-solution interfaces. These model biological membranes were used to investigate the electron transfer and lateral mobility of ubiquinone (Q10). The integrity of these types of bilayers was characterized by the analysis of the interfacial capacitance and the magnitude of the electroreduction current of Ru(NH3)6(3)+. Q10 can be incorporated in the bilayer at the electrode surface at about 5 mol.% as a component of the DPPC monolayer. Bilayer-immobilized Q10 maintains its electroactivity and can be detected electrochemically in an alkaline medium where its redox reactivity involves reversible 2e- transfer. Q10 appears to be immobile when deposited directly on the OM monolayer, but it exhibits lateral mobility when present within the OM/DPPC bilayer assembly. Its electroactivity, in both cases, is affected by the density of pinhole defects in the OM monolayer at the electrode surface.