Interaction of cupric and cadmium ions with a protein-ovalbumin (OA)

The binding of Cu and Cd ions with ovalbumin has been measured indirectly by observing the displacement of H⁺ from acidic groups on the ovalbumin. The pH-measuring procedure agreed with values obtained by an equilibrium dialysis method. Both the metals were bound by carboxyl groups with log K values being 2.39 and 2.22, respectively. The extent of binding was found to be pH dependent with the involvement of the imidazole site yielding logK values of 3.23 and 2.80, respectively. Equilibrium dialysis results supported involvement of both carboxyl and imidazole groups of the protein in metal ion binding.