Acid-base properties and copper(II) complexes of dipeptides containing histidine and additional chelating bis(imidazol-2-yl) residues

J Inorg Biochem. 2004 Jan;98(1):24-32. doi: 10.1016/j.jinorgbio.2003.09.009.

Abstract

Copper(II) complexes of dipeptides of histidine containing additional chelating bis(imidazol-2-yl) agent at the C-termini (PheHis-BIMA [N-phenylalanyl-histidyl-bis(imidazol-2-yl)methylamine] and HisPhe-BIMA [N-histidyl-phenylalanyl-bis(imidazol-2-yl)methylamine]) were studied by potentiometric, UV-Visible and Electron Paramagnetic Resonance (EPR) techniques. The imidazole nitrogen donor atoms of the bis(imidazol-2-yl)methyl group are described as the primary metal binding sites forming stable mono- and bis(ligand) complexes at acidic pH. The formation of a ligand-bridged dinuclear complex [Cu2L2]4+ is detected in equimolar solutions of copper(II) and HisPhe-BIMA. The coordination isomers of the dinuclear complex are described via the metal binding of the bis(imidazol-2-yl)methyl, amino-carbonyl and amino-imidazole(His) functions. In the case of the copper(II)-PheHis-BIMA system the [NH2, N-(amide), N(Im)] tridentate coordination of the ligand is favoured and results in the formation of di- and trinuclear complexes [Cu2H(-1)L]3+ and [Cu3H(-2)L2]4+ in equimolar solutions. The presence of these coordination modes shifts the formation of "tripeptide-like" ([NH2, N-, N-, N(Im)]-coordinated) [CuH(-2)L] complexes into alkaline pH range as compared to other dipeptide derivatives of bis(imidazol-2-yl) ligands. Although there are different types of imidazoles in these ligands, the deprotonation and coordination of the pyrrole-type N(1)H groups does not occur below pH 10.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Copper / chemistry*
  • Copper / metabolism
  • Dipeptides / chemistry*
  • Dipeptides / metabolism
  • Electron Spin Resonance Spectroscopy
  • Histidine / chemistry*
  • Histidine / metabolism
  • Hydrogen-Ion Concentration
  • Imidazoles / chemistry*
  • Kinetics
  • Ligands
  • Molecular Structure
  • Potentiometry
  • Spectrophotometry, Ultraviolet

Substances

  • Dipeptides
  • Imidazoles
  • Ligands
  • Histidine
  • Copper