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

Bilayer assemblies consisting of octadecanethiol (OM) and L-alpha-dipa lmitoyl phosphatidylcholine (DPPC) were formed at the gold-solution in terfaces. These model biological membranes were used to investigate th e electron transfer and lateral mobility of ubiquinone (Q10). The inte grity 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 monolay er. Bilayer-immobilized Q10 maintains its electroactivity and can be d etected electrochemically in an alkaline medium where its redox reacti vity involves reversible 2e- transfer. Q10 appears to be immobile when deposited directly on the OM monolayer, but it exhibits lateral mobil ity when present within the OM/DPPC bilayer assembly. Its electroactiv ity, in both cases, is affected by the density of pinhole defects in t he OM monolayer at the electrode surface.