Application of a novel 1:1 gold(I)-chromophoric thiolate complex as a spectrophotometric probe for the thiol-exchange reactions of anti-arthritic gold drugs in biological fluids

Abstract

An oligomeric 1:1 gold(I) complex of the chromophoric thiol 5-mercapto (2-nitrobenzoate) has been synthesized and applied as a spectrophotometric probe for the thiol-exchange reactions of structurally-analogous 1:1 gold(I)-thiolate drugs. For low-molecular-mass thiols, results were consistent with the initial formation of a monomeric mixed-ligand bis-thiolato gold(I) complex followed by further ligand substitution by excess thiol to produce 5-mercapto (2-nitrobenzoate) and a monomeric bis-thiolato gold(I) complex. For human serum albumin, however, the spectrophotometric changes were only consistent with the binding of gold(I) to its single cysteine residue (Cys-34) with the retention of the 5-mercapto (2-nitrobenzoate) ligand on gold(I).