On the Adsorption of Glucose Oxidase at a Gold Electrode

In this paper, the shape and size of glucose oxidase (GO) adsorbed on a gold electrode was determined by ellipsometry. It was concluded that GO is a prolate ellipsoid molecule with a major axis of 140Å and a minor axis of 50Å. Two orientations of the molecule on the surface were observed: the major axis can be perpendicular to the surface (standing position) or parallel to the surface (lying position). Above a certain coverage, enzymes in the standing position are not stable and undergo a transition to the lying position due to increasing intermolecular interaction. In the lying position, the enzyme‐and‐substrate contact area is large, and gradual unfolding occurs, leading to a significant change in the structure of the protein. It was possible to detect direct electron transfer between a gold electrode and glucose oxidase. After a short contact time, two almost overlapping electron transfer processes were distinguished, but were gradually transformed to a single response that was characteristic for adsorbed FAD, thus showing that significant changes in the protein structure occur, leading the deactivation of the enzyme.