Charge and hydration structure of dendritic polyelectrolytes: molecular simulations of polyglycerol sulphate

TL;DR

This study uses molecular dynamics simulations to analyze the charge, hydration, and structural properties of dendritic polyglycerol sulphate, highlighting charge renormalization effects and comparing different simulation approaches for biomedical applications.

Contribution

It provides detailed insights into the charge and solvation structure of dendritic polyglycerol sulphate using explicit-solvent molecular dynamics, addressing effective charge determination and comparing simulation methods.

Findings

Consistent effective electrostatic size across simulation approaches.

High charge renormalization effects observed in dPGS.

Thermodynamic analysis of water insertion into dPGS.

Abstract

Macromolecules based on dendritic or hyperbranched polyelectrolytes have been emerging as high potential candidates for biomedical applications. Here we study the charge and solvation structure of dendritic polyglycerol sulphate (dPGS) of generations 0 to 3 in aqueous sodium chloride solution by explicit-solvent molecular dynamics computer simulations. We characterize dPGS by calculating several important properties such as relevant dPGS radii, molecular distributions, the solvent accessible surface area, and the partial molecular volume. In particular, as the dPGS exhibits high charge renormalization effects, we address the challenges of how to obtain a well-defined effective charge and surface potential of dPGS for practical applications. We compare implicit- and explicit-solvent approaches in our all-atom simulations with the coarse-grained simulations from our previous work. We find consistent values for the effective electrostatic size (i.e., the location of the effective charge of a Debye--H\"{u}ckel sphere) within all the approaches, deviating at most by the size of a water molecule. Finally, the excess chemical potential of water insertion into dPGS and its thermodynamic signature are presented and rationalized.