Interaction of metals with serum albumins is of special interest as it may mediate the toxic or beneficial action of metal ions and their complexes that are often considered (pro)drugs. Among metals, gold(III) draws special attention because of the antibacterial activity of its complexes reported recently. The paper focuses on the interactions between bovine and human serum albumins and gold(III) species in aqueous solutions. Tetrachloroaurate(III) hydrolysis, protein self-association and interactions involving chloride ions are accounted for to determine the most probable stoichiometric composition of gold(III) associated with proteins and the related binding constants. The data obtained are used to calculate the equilibrium composition of the solution containing [AuCl4]−, biologically active hydrazone derived from pyridoxal 5′-phosphate and bovine serum albumin at different pH values.
