Proton-magnetic-resonance study of copper(I) complexes with peptides containing sulfhydryl and imidazole groups as possible model ligands for copper proteins.

Abstract

The copper(I) complexes of peptides containing sulfhydryl and imidazole groups have been investigated in aqueous solution by proton magnetic resonance (1H NMR). The N-mercaptoacetyl-L-histidine coordinates through the sulfhydryl sulfur and imidazole nitrogen atoms to form the unique 1:1 Cu(I) complex species containing bridged imidazole. The sulfhydryl and imidazole groups are adequate ligands for not only Cu(II) but also Cu(I). The 1H NMR spectra show that the peptide nitrogen group is not involved in complex formation of Cu(I) with N-mercaptoacetyl-L-histidine and 3-mercaptopropionyl-L-histidine. The results have been discussed with respect to the protein ligands for 'blue' copper centers.