Aggregation of Beta-Amyloid Peptides Proximal to Zwitterionic Lipid Bilayers

One of the hallmarks of Alzheimers disease is the deposition of amyloid plaques, which consist of β-amyloid (Aβ) peptides in fibrillar states. Nonfibrillar Aβ aggregates have been considered as an important intermediate in the pathway of fibrillization, but little is known about the formation mechanism. The on-pathway β-sheet intermediates of Aβ40 peptides can be trapped by incubating the peptides in liposomes formed by zwitterionic lipids. The aggregates of Aβ40 peptides have been prepared at a peptide concentration of less than 10 μm. Solid-state NMR spectroscopy data show that the backbone conformation of the aggregates is almost identical to that of the fibrils formed in free solution. In contrast to anionic lipids, zwitterionic lipids, which are typical of neuronal soma, did not induce any significant conformational difference in Aβ40 fibrils. This liposome-Aβ system may serve as a useful model to study the fibril formation mechanism.