Potentiometric and spectroscopic studies on transition metal complexes of glylys(Gly) and Asp-e-Lys.

Copper(II), nickel(II) and zinc(II) complexes of the peptides GlyLys(Gly) and Asp-e-Lys, containing the amide functions at the e-amino groups of the lysyl residues were studied by potentiometric, UV-VIS and EPR spectroscopic methods. EPR spectroscopic data indicate the existence of two isomeric forms of the major complex formed in the copper(II)-GlyLys(Gly) system. The nickel(II) and zinc(II)-GlyLys(Gly) systems have been characterised by the formation of stable 1:1 complexes containing bis(amino, carbonyl) co-ordination and a macrochelate. Deprotonation and co-ordination of the amide groups were detected in the copper(II) and nickel(II) complexes. The co-ordination chemistry of Asp-e-Lys is best described by the metal binding ability of the amino acid residues and it's high affinity for dimerisation. The dinuclear complexes contain only amino acid binding sites. Deprotonation and co-ordination of the amide functions were suggested only in the copper(II)-containing systems, resulting in the formation of another dinuclear complex.