COMPETITION BETWEEN THE TERMINAL AMINO AND IMIDAZOLE NITROGEN DONORS FOR COORDINATION TO NI(II) IONS IN OLIGOPEPTIDES

Spectroscopic and potentiometric studies on Ni(II) complexes with olig opeptides containing a histidine (His) residue in the fourth position of the peptide sequence have shown that imidazole nitrogen can act as the major binding site for metal ions. As a result, coordination of Ni (II) to an imidazole nitrogen of a His residue leads to more stable sp ecies than those obtained for linear peptides containing non-coordinat ing side chains, such as tetraalanine.