Gold(III) reduction in a tris-HCl buffer: Effect of riboflavin, rutin, 1,1-dipyridyl, and 1-naphthol

Reduction of chloroauric acid on platinum and gold electrodes in a 0.1 M tris-HCl buffer of pH 8 containing riboflavin, rutin, 1,1-dipyridyl, or 1-naphthol is studied by cyclic voltammetry and in situ ESR methods. On the basis of the obtained data it is assumed that in the buffer there occurs the reduction of Au(III) to Au(I). In the presence of 1,1-dipyridyl, there occurs the reduction of complex [Au(III)-1,1-dipyridyl]. The reduction of Au(III) in the presence of 1-naphthol is realized in the composition of complex [Au(III)-tris-1-naphthol]. The hampering of the electrode process of the Au(III) reduction in the presence of 1-naphthol is caused by the adsorption of the [tris-1-naphthol] associates at the electrode surface. The presence of Au(III) does not exert any influence on the process of electroreduction of riboflavin. The obtained results make it possible to presume that the resistance of gold-accumulating cells Micrococcus luteus toward toxic compounds that are inhibitors of the respiratory chain, such as 1,1-dipyridyl and 1-naphthol, is caused by their binding in gold-containing complexes in the composition of Au-protein.