POTENTIOMETRIC AND SPECTROSCOPIC STUDIES ON THE COPPER(II) COMPLEXES OF PEPTIDE-HORMONES CONTAINING DISULFIDE BRIDGES

Copper(II) complexes of oxytocin, 4-Glu-oxytocin, 5-Asp-oxytocin, and GlyGlyGly-Lys(8)-vasopressin were studied by potentiometric, EPR, and UV-visible spectroscopic methods. The formation of 4N-coordinated comp lexes was characteristic of all ligands. This type of coordination is especially favored for oxytocin due to the specific conformation of th e ring coupled by the disulfide bridge. The coordination of the gamma- carboxylate group of 4-Glu-oxytocin and a disulfide sulfur atom of Gly GlyGly-Lys(8)-vasopressin was reported to occur in the 2N-complexes ov er medium pH range.