POTENTIOMETRIC AND VOLTAMMETRIC INVESTIGATIONS OF H-2/H+ CATALYSIS BY PERIPLASMIC HYDROGENASE FROM DESULFOVIBRIO-GIGAS IMMOBILIZED AT THE ELECTRODE SURFACE IN AN AMPHIPHILIC BILAYER ASSEMBLY

Interactions of an enzyme with an organized amphiphilic bilayer are explored as a general means of enzyme immobilization in electroenzymatic systems. Immobilization of Desulfovibrio gigas hydrogenase at the electrode surface involves hydrophobic interactions of the enzyme with the bilayer assembly consisting of octadecyltrichlorosilane and octadecylviologen (C18MV2+) molecules. Due to a hydrophobic character of the enzyme, these interactions direct the enzyme to occupy a central position in the bilayer's hydrocarbon region and lead to immobilization of 3 pmol/cm2 of the enzyme in the plane of the bilayer. This corresponds to 50% surface coverage. The immobilized enzyme catalyzes H-2 oxidation mediated by the C18MV2+/.+ couple. This electroenzymatic scheme functions under steady-state voltammetric as well as potentiometric conditions in the pH range 3.5-10. Coupling of enzymatic activity to the electrode surface is accomplished via lateral diffusion of the octadecylviologen molecules along the bilayer assembly.