# Interaction of charged patchy protein models with like-charged polyelectrolyte brushes

## TL;DR

This study uses computer simulations to explore how charged patchy proteins interact with like-charged polyelectrolyte brushes, revealing strong electrostatic attractions influenced by salt concentration and patch charge.

## Contribution

It introduces a detailed simulation analysis of patchy protein models interacting with polyelectrolyte brushes, highlighting the roles of multipolar and counterion effects.

## Key findings

- Strong binding affinities up to tens of kT observed.
- Attraction strongest at the brush surface due to multipolar and counterion effects.
- Salt concentration and patch charge significantly influence adsorption.

## Abstract

We study the adsorption of charged patchy particle models (CPPMs) on a thin film of a like-charged and dense polyelectrolyte (PE) brush (of 50 monomers per chain) by means of implicit-solvent, explicit-salt Langevin dynamics computer simulations. Our previously introduced set of CPPMs embraces well-defined one-, and two-patched spherical globules, each of the same net charge and (nanometer) size, with mono- and multipole moments comparable to those of small globular proteins. We focus on electrostatic effects on the adsorption far away from the isoelectric point of typical proteins, i.e., where charge regulation plays no role. Despite the same net charge of the brush and globule we observe large binding affinities up to tens of the thermal energy, kT, which are enhanced by decreasing salt concentration and increasing charge of the patch(es). Our analysis of the distance-resolved potentials of mean force together with a phenomenological description of all leading interaction contributions shows that the attraction is strongest at the brush surface, driven by multipolar, Born (self-energy), and counterion-release contributions, dominating locally over the monopolar and steric repulsions.