Spontaneous β-barrel formation:: An all-atom Monte Carlo study of Aβ16-22 oligomerization

Using all-atom Monte Carlo simulations with implicit water, combined with a cluster size analysis, we study the aggregation of A beta(16-22), a peptide capable of forming amyloid fibrils. We consider a system of six initially randomly oriented A beta(16-22) peptides, and investigate the thermodynamics and structural properties of aggregates formed by this system. The system is unaggregated without ordered secondary structure at high temperature, and forms beta-sheet rich aggregates at low temperature. At the crossover between these two regimes, we find that clusters of all sizes occur, whereas the beta-strand content is low. In one of several runs, we observe the spontaneous formation of a beta-barrel with six antiparallel strands. The beta-barrel stands out as the by far most long-lived aggregate seen in our simulations.