Electrochemical Monitoring of Reduction and Binding of Iron Amyloid-β Complexes at Boron-Doped Diamond Electrode

The amino acid residues for reduction and binding of amyloid–β peptide (Aβ)–Fe(III) complexes were investigated mainly by voltammetry at boron-doped diamond electrodes. Distinguished from natural Fe(III)–Aβ(1–16) complex, the recovering redox behavior of Fe(III)–Aβ(Y–F) complex showed higher free-ion concentration and weaker bonding ability, evidencing that Fe(III) primarily binded to Aβ via Tyr10. Whereas, there were no detectable distinctions in electroactivity along with UV/vis absorptivity and fluorescence quenching between Fe(III)–Aβ(1–16) and Fe(III)–Aβ(H–N), which indicates that three His were eliminated in direct bonding to Fe(III). Compared with Fe–Aβ(1–16), the significant enhancement of Ip (Fe(II)-Fe(0)) in Fe–Aβ(1–42), Fe–Aβ(25–35), and even the exogenous Met to Fe(III) provided electrochemical evidences that the reduction of Fe(III) to Fe(II) was aroused by Met directly. Zn(II) which was redox-silent, also contributed the pathogenesis but can not affect the redox signal of Fe(III)–Aβ.