Ag/AgCl at pH 7.4. The tyrosyl radical that is formed undergoes hydrolysis and the obtained orthoquinone can later be reduced to a catechol in a two-electron and two-proton process. Voltammetry is also useful for studying metal-induced conformational changes of Aβ (1-x) as well as Aβ(1-x)-Cu(II) complexes, which are formed in the presence of Cu ions in the brain. For Aβ (1-16), in the presence of Cu(II) ions, a decrease of the tyrosine oxidation peak current and a shift of the oxidation potential to more positive potentials has been observed. This suggests that the structure of the peptide changes significantly upon complexation of these metal cations.