Link between Affinity and Cu(II) Binding Sites to Amyloid-β Peptides Evaluated by a New Water-Soluble UV–Visible Ratiometric Dye with a Moderate Cu(II) Affinity

International audienceBeing able to easily determine the Cu(II) affinity for biomolecules of moderate affinity is important. Such biomolecules include amyloidogenic peptides, such as the well-known amyloid-β peptide involved in Alzheimer’s disease. Here, we re-port the synthesis of a new water soluble ratiometric Cu(II) dye with a moderate affinity (10^9 M-1 at pH 7.1) and the characterizations of the Cu(II) corresponding complex by X-ray crystallography, EPR and XAS spectroscopic methods. UV-Vis competition were performed on the Aβ peptide as well as on a wide series of modified peptides, leading to an affinity value of 1.6 10^9 M-1 at pH 7.1 for the Aβ peptide and to a coordination model for the Cu(II) site within the Aβ peptide that agrees with the one mostly accepted currently