Thermodynamics of Peptide Aggregation Processes. An Analysis from Perspectives of Three Statistical Ensembles

TL;DR

This paper investigates peptide aggregation as a phase separation process using a mesoscopic model and multicanonical Monte Carlo simulations, revealing detailed thermodynamic insights especially from a microcanonical perspective.

Contribution

It introduces a comprehensive analysis of peptide aggregation across three statistical ensembles, highlighting the microcanonical approach's advantages in small system phase transitions.

Findings

Peptide aggregation resembles a phase separation process.

Microcanonical entropy shows a convex intruder indicating surface effects.

Microcanonical analysis reveals details not accessible via temperature control.

Abstract

We employ a mesoscopic model for studying aggregation processes of protein-like 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 nonnegligible 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.