Polarographic and pH-metric studies on the interaction of lead with transfusion gelatin

Abstract

Polarographic and- pH-metric studies of mixtures containing lead- nitrate and transfusion gelatin were undertaken to ascertain how plumbous ions were bound to the protein. Experiments carried out with varying concentrations of the reactants at a fixed ionic strength; and.under vaying pH conditions have shown the existence of a metal-protein complex in the pH range 3.7–5.57. Experiments carried out at a higher pH range (5.9–6.8) gave little or no evidence for the binding of lead to the imidazole groups. An alternative procedure, identical in principle with BJERRUM's method, was employed to calculate V m from the difference in hydrogen ion data in the presence and absence of metal. Evidence is presented for a one-to-one binding of plumbous ion to the carboxylate ion of transfusion gelatin, for which the intrinsic association constant was calculated as 1.87 and the free energy change of the combination as −2.593 kcal.