  The intrinsic property of proteins to form structural motifs such as
alpha-helices and beta-sheets leads to a complex phase behavior in which
proteins can assemble into various types of aggregates including crystals,
liquidlike phases of unfolded or natively folded proteins, and amyloid fibrils.
Here we use a coarse-grained protein model that enables us to perform Monte
Carlo simulations for determining the phase diagram of natively folded
alpha-helical and unfolded beta-sheet forming peptides. The simulations reveal
the existence of various metastable peptide phases. The liquidlike phases are
metastable with respect to the fibrillar phases, and there is a hierarchy of
metastability.
