An integrated study of the affinities of the Aβ16 peptide for Cu(I) and Cu(II): Implications for the catalytic production of reactive oxygen species

Abstract

A new fluorescent probe Aβ16wwa based upon the Aβ16 peptide has been developed with two orders of magnitude greater fluorescence intensity for sensitive detection of interactions with Cu(II). In combination with the Cu(I) probe Ferene S, it is confirmed that the Aβ16 peptide binds either Cu(I) or Cu(II) with comparable affinities at pH 7.4 (logKID = -10.4; logKIID = -10.0). It follows from this property that the Cu-Aβ16 complex is a robust if slow catalyst for the aerial oxidation of ascorbate with H2O2 as primary product (initial rate, ∼0.63 min-1 for Cu-Aβ16 versus >2.5 min-1 for Cuaq2+). An integrated study of variants of this peptide identifies the major ligands and binding modes involve..