The direct electrochemical oxidation of synthetic peptides analogous to the amyloid-beta (Aโ) implicated in the
pathogenesis of Alzheimer's disease has been demonstrated on carbon screen-printed electrodes in the phosphate
buffer (pH 7.2) by using square wave voltammetry. The full-length peptide Aโ42 was found to produce
two peaks at potentials of 0.6, 1.05, and a wave at about 1–1.5 V (vs. Ag/AgCl) assigned, respectively, to its Tyr,
His, and Met residues. The correspondence between the oxidation signals and the appropriate residues was
established based on the analysis of voltammograms obtained for the free Tyr, His, and Met amino acids; for
the Aโ16 peptide (representing the Aโ metal-binding domain and lacking the Met residue); for Aโ16 mutants
differing in the number of His residues; and for the rat Aโ16 lacking the Tyr residue. The oxidation signals
were found to be proportional to the amino acid and peptide concentrations. The observed difference in the electrochemical
behavior of Aโ peptides widens the application of direct electrochemistry to peptide differentiation
and point mutation studies as well as to investigation of Aโ aggregation and complexing