Coagulation of zinc-modified hemoglobin

At a sufficiently high concentration of bovine oxyhemoglobin, the effect Zn(II) ions exert on its coagulation compares with that of Hg(II) ions. It is suggested that the center of preferential stoichiometric binding with Zn(II) ions in the protein is the sulfur atom of reactive SH groups. However, the binding of Zn(II) ions with groups other than thiolic equally affects the protein aggregation. Analysis of the pH dependence of the protein aggregation rate showed that the most likely alternative binding centers are histidine residues of the protein.