Tyrosine Based Electrochemical Analysis of Amyloid-p Fragment (1-16) Binding to Metal(II) Ions

Electrochemical oxidation of the synthetic peptide A beta(1-16), representing the metal-binding domain of Alzheimer's human amyloid-beta peptide, was investigated on carbon screen printed electrodes. The electrochemical behavior of A beta(1-16), determined by the oxidation of the single Tyr-10 residue, was compared with that of free Tyr and with Tyr-lacking rat A beta(1-16). The A beta(1-16) oxidation signal detected at the potential of about 0.6V (vs. Ag/AgCl) was used for monitoring peptide interactions with metal ions. For this purpose, four vitally important metal ions (Zn(II), Cu(II), Mg(II), and Ca(II)) were tested with respect to their binding to A beta(1-16) within a wide range of ion concentrations in Tris-buffers with pH values from 5 to 9. Addition of both Zn(II) and Cu(II) ions significantly reduced the intensity of the A beta(1-16) oxidation signal and shifted the peak to more positive potentials, while Mg(II) and Ca(II) ions had no noticeable effect. The results of electrochemical analysis of the metal(II)-A beta(1-16) complexes were in good agreement with the literature data obtained by other methods. The proposed electrochemical assay based on the direct oxidation signal of a Tyr residue appears to be very promising for monitoring the metal-induced conformational changes of amyloid-beta peptides in vitro as well as for studying other metal ion-protein complexes. (C) 2015 Elsevier Ltd. All rights reserved.