Copper(ii), nickel(ii) and zinc(ii) complexes of the peptides GlyLys(Gly) and Asp-ε-Lys, containing the amide functions at the ε-amino groups of the lysyl residues were studied by potentiometric, UV-VIS and EPR spectroscopic methods. The stoichiometry of the major species formed in the copper(ii)â GlyLys(Gly) system is [CuHâ 1L] and the EPR spectroscopic data indicate the existence of two isomeric forms of the complex. The nickel(ii) and zinc(ii)â GlyLys(Gly) systems have been characterised by the formation of stable [ML]⁺ complexes containing bis(NH2,CO) 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-ε-Lys is best described by the metal binding ability of the amino acid residues and it's high affinity for dimerisation. The stoichiometry of the dinuclear complexes can be given as [M2L2], containing 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 the [Cu2Hâ 2L2]^2â dinuclear complex.