Coordination of copper(II) ions by the 11–20 and 11–28 fragments of human and mouse β-amyloid peptide

Abstract

A potentiometric and spectroscopic (UV–vis, CD and EPR) study of Cu(II) binding to the (11–20), (11–28), (Ac-11-20H) and (Ac-11-28) fragments of human (H) and mouse (M) β-amyloid peptide was carried out. The values of the protonation constants of the two lysine side chain amino groups for the (11–28) and (Ac-11–28) fragments of β-amyloid peptide differ noticeably suggesting considerable interactions between the two residues. The N-terminal amino acid sequence Xaa–Yaa–His for the (11–20H) and (11–28H) fragments determines the coordination ability of the fragments studied to copper(II) ions. Addition of the (17–20) and (17–28) sequences to the (11–16) fragment of human and mouse β-amyloid peptide does not change the coordination mode, and the stabilities of the complexes formed are comparable to those of the (11–16) peptide, although 1N complexes of the (11–28) fragments are stabilized by about one order of magnitude compared to those of the (11–16) peptides. The (Ac-11–28) peptides form complexes with the same coordination mode as those for the (Ac-11–16) fragments. The stability of the complexes for the (Ac-11–28H) fragment is one or two orders of magnitude higher compared to those of the (Ac-11–16H) fragment. This stabilization may result from structural organization of a peptide in copper(II) complexes.