A closer look at arrested spinodal decomposition in protein solutions

TL;DR

This study investigates how protein solutions undergo arrested spinodal decomposition, forming gel-like networks with specific structural properties, influenced by temperature and concentration, revealing critical scaling behavior during the process.

Contribution

It provides detailed experimental insights into the arrested spinodal decomposition in protein solutions, linking structural features to phase separation dynamics and arrest conditions.

Findings

Solid-like structures form bicontinuous networks

Correlation length follows critical scaling near spinodal

Arrest occurs when dense phase volume fraction intersects arrest threshold

Abstract

Concentrated aqueous solutions of the protein lysozyme undergo a liquid solid transition upon a temperature quench into the unstable spinodal region below a characteristic arrest temperature of Tf=15C. We use video microscopy and ultra-small angle light scattering in order to investigate the arrested structures as a function of initial concentration, quench temperature and rate of the temperature quench. We find that the solid-like samples show all the features of a bicontinuous network that is formed through an arrested spinodal decomposition process. We determine the correlation length Xi and demonstrate that Xi exhibits a temperature dependence that closely follows the critical scaling expected for density fluctuations during the early stages of spinodal decomposition. These findings are in agreement with an arrest scenario based on a state diagram where the arrest or gel line extends far into the unstable region below the spinodal line. Arrest then occurs when during the early stage of spinodal decomposition the volume fraction phi2 of the dense phase intersects the dynamical arrest threshold phi2Glass, upon which phase separation gets pinned into a space-spanning gel network with a characteristic length Xi.