CU(II) BINDING BY ANGIOTENSIN-II FRAGMENTS - ASP-ARG-VAL-TYR-ILE-HIS AND ARG-VAL-TYR-ILE-HIS - COMPETITION BETWEEN AMINO GROUP AND IMIDAZOLE NITROGENS IN ANCHORING OF METAL-IONS

Potentiometric and spectroscopic (absorption, circular dichroism and e lectron paramagnetic resonance) study on the coordination of two angio tensin II fragments (Asp-Arg-Val-Tyr-Ile-His and Arg-Val-Tyr-Ile-His) to Cu(II) ions has shown that competition between amino and imidazole nitrogens to anchor metal ions is a complicated process and may lead t o formation of macrochelate rings. The important factor that influence s this competition is the distance between competing His and N-termina l residues (number of spacer residues in a peptide sequence).