Protein crystals and charged surfaces: interactions and heterogeneous nucleation

TL;DR

This paper investigates how electrostatic interactions between charged protein crystals and charged surfaces influence nucleation, showing that oppositely charged surfaces can promote crystal formation by reducing the nucleation energy barrier.

Contribution

It provides a quantitative calculation of electrostatic interactions and demonstrates how charged surfaces can serve as nucleation sites for protein crystals.

Findings

Oppositely charged surfaces attract protein crystals, lowering nucleation barriers.

Like-charged surfaces repel protein crystals, inhibiting nucleation.

Electrostatic interactions can be several kT per protein molecule, significantly affecting nucleation processes.

Abstract

As proteins typically have charges of around 10, they will interact strongly with charged surfaces. We calculate the electrostatic contribution to the interaction of crystals of protein with charged surfaces. The surfaces repel like-charged crystals and attract oppositely-charged crystals, with free energies which can be easily several kT per protein molecule brought into contact with the surface. This means that oppositely charged surfaces can act as a nucleant, they can induce nucleation of a protein crystal by lowering the free energy barrier to heterogeneous nucleation of the crystal from a dilute solution.