Bio-electrochemistry

Abstract

Direct electron transfer reactions of redox proteins at a variety of electrodes, including modified gold, pyrolytic graphite and ruthenium oxide, are discussed. It is stressed that the electron transfer occurs without mediation. For many redox proteins, the rate of the electron transfer depends critically on the presence in solution or, to be more correct, at the electrode surface, of di-, tri- or even tetravalent metal ions or complexes. The dependence on the type of promoter used to modify the gold surface, the nature of complexes formed with added metal salts and the structures of the adsorbed redox protein are examined. In instances where direct electron transfer is very slow, as is the case at present with many potentially useful enzymes, indirect mediated electron transfer is used. Of particular value as mediators are ferrocenes, not only because they take part in rapid, reversible electrochemistry but because of the wide variety of compounds that can be prepared. Their use in a variety of sensors is illustrated in electrochemical assays for glucose, ATP, creatine kinase, hydrogen peroxide, cholesterol and their application in electrochemical immunoassays is illustrated by the analysis of the drug, lidocaine. © 1987, Walter de Gruyter. All rights reserved.