Dual role of Cu2+ ions on the aggregation and degradation of soluble Aβ oligomers and protofibrils investigated by fluorescence spectroscopy and AFM

► Fluorescence and AFM studies show that copper(II) ions induce both aggregation and oxidative damage of amyloid β. ► The early stages of the formation of amyloid β fibrils have been clearly observed by AFM. ► Tyrosine fluorescence quenching by copper(II) ions allows to study the effect of this metal on amyloid β.