Impact of alpha-hydroxymethylserine (HmS) residue on the binding ability of the histidyl residue in the HmS-His dipeptide towards Cu-II, Ni-II and Zn-II

Potentiometric and spectroscopic data have shown that alpha-hydroxymethylse rylhistidine is a very efficient ligand for Cu-II, Ni-II and Zn-II. The sta bilities of the complexes formed are considerably higher than those obtaine d for Gly-His or Ala-His dipeptides. Copper(II) and Ni-II form very stable tetrameric complexes M4H-8L4. According to H-1 NMR spectra the nickel tetra meric complex is of C-2 symmetry with two pairs of different imidazole ring s. Zinc(II), on the other hand, forms only monomeric species but due to the second His residue it forms very stable ZnH-1L species via a {NH2,N-amide( -),N-imidazole} donor set.