Gelation dynamics upon pressure-induced liquid-liquid phase separation in a water-lysozyme solution

TL;DR

This study uses X-ray photon correlation spectroscopy to analyze the gelation process in a water-lysozyme solution during pressure-induced liquid-liquid phase separation, revealing detailed dynamics and the formation of a gel network.

Contribution

It provides the first detailed kinetic and dynamic characterization of pressure-induced LLPS in a protein solution, demonstrating gelation at the phase boundary with specific dynamic signatures.

Findings

System reaches phase boundary without arrest.

Coarsening slows with deeper quenches.

Dynamics show superdiffusive and subdiffusive behaviors.

Abstract

Employing X-ray photon correlation spectroscopy we measure the kinetics and dynamics of a pressure-induced liquid-liquid phase separation (LLPS) in a water-lysozyme solution. Scattering invariants and kinetic information provide evidence that the system reaches the phase boundary upon pressure-induced LLPS with no sign of arrest. The coarsening slows down with increasing quench depths. The $g_2$-functions display a two-step decay with a gradually increasing non-ergodicity parameter typical for gelation. We observe fast superdiffusive ($\gamma \geq 3/2$) and slow subdiffusive ($\gamma < 0.6$) motion associated with fast viscoelastic fluctuations of the network and a slow viscous coarsening process, respectively. The dynamics age linear with time $\tau \propto t_\mathrm{w}$ and we observe the onset of viscoelastic relaxation for deeper quenches. Our results suggest that the protein solution gels upon reaching the phase boundary.