Diversity of kinetic pathways in amyloid fibril formation.

The kinetics of peptide oligomerization was investigated using Langevin Dynamics simulations and a coarse-grained peptide model. The simulations show a rich diversity of aggregation pathways, modulated by the beta-sheet propensity (flexibility) of the peptide. Aggregation into amyloidlike fibrils occurs via three main mechanisms: (i) formation of fibrils directly from the assembly of early ordered oligomers, (ii) fibril formation via the formation of on-pathway, nonfibrillar aggregates high in beta-sheet content, and (iii) formation of amorphous aggregates followed by reorganization to beta-sheet aggregates and to fibrils. beta-sheet, nonfibrillar aggregates also appeared as long-lived, "off-pathway" end-product species.