Studies on transition-metal–peptide complexes. Part 13. Copper(II) and nickel(II) complexes of amino acids and peptides containing a thioether group

Abstract

The stability constants of the copper(II) and nickel(II) complexes of amino acids [S-methyl-L-cysteine and methionine (Met)] and peptides [Met-Gly, Gly-Met, Met-His, and His-Met (Gly = glycine, His = histidine)] containing thioether groups have been determined. It was found that, as for the amino acids, the presence of the thioether group in the peptides (HA) has only a slight influence on the co-ordination of the ligands. For the peptides containing an N-terminal methionine residue (Met-Gly and Met-His), the axial interaction of the thioether group may be appreciable, which inhibits the formation of complexes [MA₂H_–1]^–.