Circular Dichroic Study of the Interaction of Gelatin with Palladium(n)

Abstract

AbstractThe structure of the gelatin-palladium(u) complexes formed under a variety of conditions was studied by measuring CD and absorption spectra and comparing them with those of simple peptide complexes. The complex is considered to be tetragonal and tetracoordinate. In the acid pH region the formation of two types of complexes in which palladium(n) is bound by the carboxylate group is proposed, depending on the pH and gelatin concentration. The formation of complexes in which palladium(n) is bound by each of the imidazole and amino groups is shown above around pH 4.5. In the alkaline pH region all of the carboxyl, imidazole and amino groups are involved in complexing, and palladium(u) is presumably coordinated by three peptide nitrogen donor atoms in addition to the ionizable side-group. In both acid and alkaline pH regions an additional band is observed near 260 nm in the circular dichroism spectrum, which is ascribed to the complex with one imidazole nitrogen and three peptide nitrogen donor atoms.