Solvation vs. freezing in a heteropolymer globule

TL;DR

This paper models how heteropolymer globules respond to preferential solvation, revealing that surface composition depends linearly on solvation strength and that significant surface enrichment occurs only under strong solvent preferences.

Contribution

It introduces a Gaussian energy distribution model to analyze the interplay between solvation and globule configuration in heteropolymers, highlighting the conditions for surface enrichment.

Findings

Surface composition is proportional to solvation strength in most conditions.

Large surface enrichment occurs only with very strong solvent preference.

The model explains the linear response regime due to statistical independence of energies.

Abstract

We address the response of a random heteropolymer to preferential solvation of certain monomer types at the globule-solvent interface. For each set of monomers that can comprise the molecule's surface, we represent the ensemble of allowed configurations by a Gaussian distribution of energy levels, whose mean and variance depend on the set's composition. Within such a random energy model, mean surface composition is proportional to solvation strength under most conditions. The breadth of this linear response regime arises from approximate statistical independence of surface and volume energies. For a diverse set of monomer types, the excess of solvophilic monomers at the surface is large only for very strong solvent preference, even in the ground state.