The contribution of electrostatic interactions to the collapse of oligoglycine in water

TL;DR

This study investigates how electrostatic interactions influence the collapse of oligoglycine peptides in water by simulating charge scaling and analyzing thermodynamic contributions to conformational stability.

Contribution

It provides new insights into the role of electrostatic interactions in peptide collapse, highlighting the balance between solvent exclusion and intrapeptide electrostatic effects.

Findings

Electrostatic interactions significantly affect peptide conformation.

Charge scaling alters the balance of intrapeptide and peptide-water interactions.

Electrostatic solvation free energy can be estimated during peptide collapse.

Abstract

Protein solubility and conformational stability are a result of a balance of interactions both within a protein and between protein and solvent. The electrostatic solvation free energy of oligoglycines, models for the peptide backbone, becomes more favorable with an increasing length, yet longer peptides collapse due to the formation of favorable intrapeptide interactions between CO dipoles, in some cases without hydrogen bonds. The strongly repulsive solvent cavity formation is balanced by van der Waals attractions and electrostatic contributions. In order to investigate the competition between solvent exclusion and charge interactions we simulate the collapse of a long oligoglycine comprised of 15 residues while scaling the charges on the peptide from zero to fully charged. We examine the effect this has on the conformational properties of the peptide. We also describe the approximate thermodynamic changes that occur during the scaling both in terms of intrapeptide potentials and peptide-water potentials, and estimate the electrostatic solvation free energy of the system.