Kinetic Mechanism of Amyloid-β-(16-22) Peptide Fibrillation

The kinetic mechanism of amyloid fibril formation by a peptide fragment containing seven residues of the amyloid-beta protein A beta-(16-22) was investigated. We found that the N- and C-terminal unprotected A beta-(16-22), containing no aggregation nuclei, showed rapid fibrillation within seconds to minutes in a neutral aqueous buffer solution. The fibrillation kinetics were well described by the nucleation-elongation model, suggesting that primary nucleation was the rate-limiting step. On the basis of both experimental and theoretical analyses, the aggregated nucleus was estimated to be composed of 6-7 peptide molecules, wherein the two beta-sheets were associated with their hydrophobic surfaces. Thin fibers with widths of 10-20 nm were formed, which increased their length and thickness, attaining a width of >20 nm over several tens of minutes, probably owing to the lateral association of the fibers. Electrostatic and hydrophobic interactions play important roles in aggregation. These results provide a basis for understanding the fibrillation of short peptides.

Automated summary

This study investigates the kinetic mechanism of amyloid fibril formation by a peptide fragment containing seven residues of the amyloid-beta protein Aβ-(16-22). The results show that the unprotected peptide fragment can rapidly form fibrils in a neutral aqueous buffer solution, and the fibrillation kinetics can be described by the nucleation-elongation model. The width of the fibrils increases over time, possibly due to lateral association. Electrostatic and hydrophobic interactions play important roles in the fibrillation process.