A voltammetric study of the binding of copper(II) to peptide fragments of prion

Binding of copper to three peptide fragments of prion (Cu2+ binding sites: 60–91, 92–96 and 180–193 amino acid residues) was investigated by anodic stripping voltammetry to determine the stoichiometries of Cu2+-prion peptide interactions. The method relies on the synthesis of N-terminally acetylated/C-terminally amidated peptide fragments of prion by solid-phase synthesis and direct monitoring of the oxidation current of copper in the absence and presence of each prion fragment. Titration curves of Cu2+ with Ac-PHGGGWGQ-NH2, Ac-GGGTH-NH2 and Ac-VNITKQHTVTTTT-NH2 were obtained in concentrations ranging from 8.52 × 10−7 to 5.08 × 10−6, 3.95 × 10−7 to 1.94 × 10−6 and 7.82 × 10−8 to 4.51 × 10−7 M, respectively. The acquired data were used to calculate the stoichiometries (one peptide per Cu2+ ion for all the three studied systems) and apparent dissociation constants (Kd = 4.37 × 10−8–3.50 × 10−10 M) for the three complexes.

Graphical abstractThe formation of stable complexes between Cu2+ ion and three peptide fragments of prion, with stoichiometry ratios of 1:1, were attested using anodic stripping voltammetry by following the decrease in the oxidation current of copper in the presence of each peptide and by calculating apparent dissociation constants of the reactions.Figure optionsDownload full-size imageDownload as PowerPoint slide