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Thermodynamics of peptide aggregation processes: An analysis from perspectives of three statistical ensembles.

Junghans C, Bachmann M, Janke W

Institut für Theoretische Physik and Centre for Theoretical Sciences (NTZ), Universität Leipzig, Postfach 100920, D-04009 Leipzig, GermanyMax-Planck-Institut für Polymerforschung, Ackermannweg 10, D-55128 Mainz, GermanyComputational Biology and Biological Physics Group, Department of Theoretical Physics, Lunds Universitet, Sölvegatan 14A, SE-223 62 Lund, Sweden.

We employ a mesoscopic model for studying aggregation processes of proteinlike hydrophobic-polar heteropolymers. By means of multicanonical Monte Carlo computer simulations, we find strong indications that peptide aggregation is a phase separation process, in which the microcanonical entropy exhibits a convex intruder due to non-negligible surface effects of the small systems. We analyze thermodynamic properties of the conformational transitions accompanying the aggregation process from the multicanonical, canonical, and microcanonical perspective. It turns out that the microcanonical description is particularly advantageous as it allows for unraveling details of the phase-separation transition in the thermodynamic region, where the temperature is not a suitable external control parameter anymore.

Published 4 March 2008 in J Chem Phys, 128(8): 085103.
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