Interaction of Hg(II) with tetrapeptides containing cysteinyl and histidinyl residues

Abstract

The mercury(II) complexes [(Boc-Cys-Ser-Ala-Cys-NH 2) 2Hg 2Cl]Na·4H 2O ( 1), (Boc-Cys-Ser(Bzl)-Ala-Cys-NH 2) 2Hg 3Cl 2 ( 2), (Boc-Cys-Ser(Bzl)-Ala-Cys-NH 2)Hg 2Cl 2 ( 3), [(Boc-Cys-Gly-Ala-Cys-NH 2) 2Hg 2Cl]Na·3H 2O ( 4), (Boc-Cys-Gly-Ala-Cys-OCH 3) 2Hg 4Cl 2·2H 2O ( 5), (Boc-Cys-Gly-Ala-Cys-OCH 3)Hg 2Cl 2·2H 2O ( 6), (Boc-His-Ser(Bzl)-Ala-Cys-NH 2)Hg 2Cl 2 ( 7) and [(Boc-His-Ser(Bzl)-Ala-Cys-NH 2)Hg 2Cl 2]Cl ( 8) were synthesized from HgCl 2 and the corresponding free or S-acetamidomethyl (Acm) and N un-Boc protected peptides, by different synthetic routes, Acm and N un-Boc protecting groups are removed upon mercury(II) coordination, while the Bzl group was removed selectively prior to reactions of the peptides with mercury(II). The peptides and the complexes formed were characterized by elemental analysis, conductivity measurements, IR, UV, and 1D and 2D 1H and 13C NMR spectroscopies. In addition, 199Hg NMR experiments suggest that mercury(II) ions exchange rapidly between chloride ions and imidazole nitrogens. Conformational studies of the peptides in the complexes formed, by ROESY experiments, suggested macromolecular chelate structures with mercury(II).