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Universal features of the peptide aggregation process suggest a common
mechanism, with a first-order phase transition in aqueous solutions of the
peptides being the driving force. Phase transitions may be strongly
affected by the small system size. Our simulation studies show that the
oversaturated aqueous solution of the amyloidogenic peptides (fragments
FLVHS of human IAPP) show two distinct stable states: one state contains a
peptide aggregate, in the other state the aggregate is noticeably
dissolved. The first state is relevant for macroscopic systems, whereas
the second one is possible in small systems only. At a fixed
concentration, the aggregate state vanishes upon decreasing the system
size. The effect observed may be one of the factors responsible for the
difference between intracellular and extracellular aggregation and
fibrillization of polypeptides. Surface effects also can strongly affect
peptide aggregation. We have studied the general effect of surface
hydrophobicity/hydrophilicity on the aggregation of peptides by
simulations of the oversaturated aqueous solutions of hydrophobic
(fragments NFGAIL of human IAPP) and hydrophilic (fragments GNNQQNY of
yeast prion Sup35) peptides near hydrophobic (paraffs in-like) and
hydrophilic (silica-like) walls. Strong adsorption of peptides is observed
in the case of the hydrophobic peptides near a hydrophobic surface only,
whereas in all other cases peptides are repelled from the surface. The
obtained results should help to find effective methods for manipulating
peptide aggregation and adsorption.
