Proton nuclear magnetic resonance studies of the complexation of zinc(II) with glycyl-L-histidylglycine.

J Ueda, A Hanaki, N Yoshida, T Nakajima

Index: Chem. Pharm. Bull. 43(12) , 2042-7, (1995)

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Abstract

The complexation of Zn(II) with glycyl-L-histidylglycine and its deuterated derivatives, glycyl-d2-L-histidylglycine and glycyl-L-histidylglycine-d2, was studied by proton nuclear magnetic resonance spectroscopy over the pD range, from 3.4 to 11.0, at 25 degrees C. Addition of Zn(II) to the peptide made the resonances of both imidazole C2-H and C4-H and both methylene-protons of glycyl residues at the amino-terminal and carboxylate end split to three lines in the pD range above 7.0. From the behavior of the C2-H and C4-H chemical shifts, formation of at least two species, in which the imidazole and amino nitrogens coordinated to the metal ion forming a chelate ring, was suggested. Those two species, the ratio of which varied depending on the total concentrations of complexes, seemed to be interconvertible; one referred to as B is a monomer and the other, referred to as C, may be a dimeric or polymeric complex.