Peculiar features of the aggregation effect of silver(I) ion on hemoglobin

Silver(I) ion has been shown to produce aggregation effect on bovine oxyhemoglobin (HbO(2)) in Tris buffer even when taken in amounts corresponding to only two or less silver ions per one HbO(2) tetramer. The extent of produced effect is comparable to those previously observed for Hg(II), Cd, Zn, and Ni in spite of significantly different electronic configurations of the ions in question. Aggregation effect of the silver is ascribed to an interaction of the reactive thiol group sulfur-bound silver atom with the carboxylate residues surrounding the reactive thiol group-bearing cysteine beta93 group of hemoglobin. Mercury ligands, in particular, Tris molecules and OH(-) anions markedly suppress the protein coagulation, thereby supporting the proposed protein aggregation mechanism.