Amyloid-beta – copper interaction studied by simultaneous nitrogen K and copper L2,3 edge soft X-ray absorption spectroscopy

Summary We study the interaction between the Aβ peptides and Cu and Zn metal ions by using soft X-ray absorption spectroscopy. The spectral features of the peptides and the Cu are simultaneously characterized by recording spectra at the N K edge and at the Cu L2,3 edges. In the presence of the peptides, the Cu L2,3 edge shows a fingerprint of monovalent Cu(I), caused by the interaction with the peptides. The appearance of Cu(I) is less significant at an acidic pH than at a basic pH. Furthermore, aggregation leads to a smaller signature of Cu(I). N K edge spectra reveal that Cu and Zn ions exhibit a different coordination with the nitrogen atoms in the peptides. This suggests different roles of Cu and Zn in the peptide aggregation. Our work provides physical insight into the participation of the metal ions and Aβ in the toxic reactive oxygen species formation.