Transient formation of intermediate conformational states of amyloid-β peptide revealed by heteronuclear magnetic resonance spectroscopy.

A detailed analysis of the NMR spectra of amyloid-β (Aβ) peptide revealed a decrease in signal intensity at higher temperature, due to a reversible conformational change of the molecule. Although peak intensity did not depend on peptide concentrations, the intensity in the region from D23 to A30 depended significantly on temperature. During the early stages of Aβ aggregation, each molecule might adopt transiently a turn conformation at around D23-A30, which converts mutually with a random coil. Stabilization of a turn by further conformational change and/or molecular association would lead to the formation of a "nucleus" for amyloid fibrils.