The cyclopeptides with the multi-His motif as ligands for copper(II)

Abstract

The coordination properties of cyclic octapeptides with multi-His motif: c(His-Gly-His-Xaa-His-Gly-His-Xaa) where Xaa=Asp or Lys, were investigated. The binding abilities of this peptides towards Cu(II) ions were studied by using different analytic methods as: potentiometry, spectroscopy and mass spectrometry. The obtained results show that the studied peptides in physiological related pH prefer formation of the species with the {4NIm} binding mode. The efficiency of Cu(II) binding depends on additional side chain groups Asp or Lys. Additionally the analysis of results for His containing cyclopeptides with different numbers of amino acid residues in cyclopeptide ring e.g. four, eight shows that in higher pH in both cases the binding by four amide nitrogens is not observed in the case of α-amino acid peptides.