An effective long-range attraction between protein molecules in solutions studied by small angle neutron scattering

TL;DR

This study uses small angle neutron scattering to reveal a weak, long-range attraction between protein molecules in solution, influenced by ion type and concentration, which extends beyond electrostatic repulsion.

Contribution

It demonstrates the existence of a long-range attraction between proteins in solution and links it to ion effects, expanding understanding of protein interactions in solution.

Findings

Long-range attraction observed in protein solutions.

Interaction range exceeds electrostatic screening.

Ion type and concentration affect protein interactions.

Abstract

Small angle neutron scattering intensity distributions taken from cytochrome C and lysozyme protein solutions show a rising intensity at very small wave vector, Q, which can be interpreted in terms of the presence of a weak long-range attraction between protein molecules. This interaction has a range several times that of the diameter of the protein molecule, much greater than the range of the screened electrostatic repulsion. We show evidence that this long-range attraction is closely related to the type of anion present and ion concentration in the solution.