Amyloid-β (Aβ) self-assembly into cross-β amyloidfibrils is implicated in a causative role in Alzheimer’s disease pathology.Uncertainties persist regarding the mechanisms of amyloid self assembly and the role of metastable prefibrillar aggregates. Aβ fibrilsfeature a sheet-turn-sheet motif in the constituent β-strands; as such, turn nucleation has been proposed as a rate-limiting step in the se...