Freezing Transition of Compact Polyampholytes

TL;DR

This paper investigates the freezing transition of polyampholytes, revealing how Coulomb interactions influence their phase behavior and implications for protein folding and evolution.

Contribution

It demonstrates that screened Coulomb interactions cause polyampholytes to freeze in a manner similar to the Random Energy Model, providing insights into protein sequence organization.

Findings

Polyampholytes exhibit REM-like freezing when charges are screened.

Coulomb interactions significantly affect the folding behavior of weakly charged proteins.

Charged amino acid sequences in proteins are non-random, influenced by Coulomb effects.

Abstract

Polyampholytes (PAs) are heteropolymers with long range Coulomb interactions. Unlike polymers with short range forces, PA energy levels have non-vanishing correlations and are thus very different from the Random Energy Model (REM). Nevertheless, if charges in the PA globule are screened as in a regular plasma, PAs freeze in REM fashion. Our results shed light on the potential role of Coulomb interactions in folding and evolution of {\it proteins}, which are weakly charged PAs, in particular making connection with the finding that sequences of charged amino acids in proteins are not random.