Characteristics of a new catalytic hydrogen current observed with albumin in the presence of cobalt(III) or (II) at the hanging mercury drop electrode

Abstract

When the hanging mercury drop electrode (HMDE) is placed in a solution which is 0.1 M in ammonia and 0.1 M in ammonium chloride and about 5 to 10×10 −4 M in cobalt(III)-hexamine or cobalt(II) chloride and in very small concentrations of bovine serum albumin (BSA), the protein is slowly adsorbed. When the adsorption is highly incomplete and the HMDE is kept for 30 s at about −1.05 V vs. SCE, “active cobalt’ is deposited as a complex (Co(0)BSA). This is anodically oxidized at about 0.0 V to unstable Co(I)BSA). When the electrode is then rapidly (500 mV s −1) cathodized, a catalytic hydrogen current ( i c) with peak at circa −1.45 V is observed. In this way it is even possible to detect and estimate BSA in concentrations of the order of 10 −12 M. A detailed study has been made of the characteristics of i c under several conditions. “Active cobalt” on the HMDE does not affect Brdička currents. Cystine and cysteine also yield the catalytic hydrogen current i c under the same conditions as does BSA.