X-ray spectroscopy study of the Cu(II)GHK peptide complex

The Cu(II)–Gly–His–Lys (Glycyl–Histidyl–Lysine) complex is of interest as a model peptide to test the methodology for studying the structure of metal sites in proteins, in particular, the copper binding site in amyloid-β. X-ray absorption spectra of the Cu(II)GHK aqueous solution are measured. The stability of the complex under X-ray radiation is controlled by optical spectroscopy. The structural models with different copper site coordination constructed based on the crystallographic structure are considered. Two optimal models are selected from the analysis of the theoretical X-ray absorption spectra of the constructed structures. The structural parameters of the selected models are optimized. It is found that the spectrum of the five-coordinated model with water molecules in the equatorial and axial positions “down” (with Cu–O distances of 1.97 Å and 2.31 Å respectively) has the best agreement with the experiment.