Aggregation of $β$-amyloid fragments

The authors study the folding and aggregation of six chains of the $β$-amyloid fragment 16–22 using Monte Carlo simulations. While the isolated fragment prefers a helical form at room temperature, in the system of six interacting fragments one observes both parallel and antiparallel $β$ sheets below a crossover temperature $Tx≈420K$⁠. The antiparallel sheets have lower energy and are therefore more stable. Above the nucleation temperature the aggregate quickly dissolves into widely separated, weakly interacting chains.