Interplay between Glass Formation and Liquid–Liquid Phase Separation Revealed by the Scattering Invariant

Abstract

The interplay of the glass transition with liquid− liquid phase separation (LLPS) is a subject of intense debate. We use the scattering invariant Q to probe how approaching the glass transition affects the shape of LLPS boundaries in the temperature/volume fraction plane. Two protein systems featuring kinetic arrest with a lower and an upper critical solution temperature phase behavior, respectively, are studied varying the quench depth. Using Q we noninvasively identify system-dependent differences for the effect of glass formation on the LLPS boundary. The glassy dense phase appears to enter the coexistence region for the albumin−YCl 3 system, whereas it follows the equilibrium binodal for the γ-globulin−PEG system.

Automated matching of two-time X-ray photon correlation maps from protein dynamics with Cahn-Hilliard type simulations using autoencoder networks

“…This line bends towards the spinodal line resulting in lower concentrations of the dense phase for deeper quenches. Such a behavior of the glass line into the coexistence region has also been observed for the LLPS of BSA − YCl 3 [18], lysozyme [14] and for γ-globulin [16].…”

“…This microscopic deaccceleration can eventually lead to the arrest of phase separation on larger length scales complemented by the formation of bicontinuous gel network structures -as observed in colloidal and protein systems [9][10][11]. Employing time resolved scattering experiments the kinetics during arrested phase separations have been observed frequently as a slowdown of the growth of static structure factor S(Q) both in Qposition and peak height for low temperature quenches [12][13][14][15][16][17][18]. In contrast, the dynamics of protein solutions evolving into an arrested phase transition is still elusive as it requires the concurrent monitoring of an extraordinarily broad range of time and length scales.…”

Kinetics of Network Formation and Heterogeneous Dynamics of an Egg White Gel Revealed by Coherent X-Ray Scattering

“…We first investigate the growth kinetics of the gel aggregates by calculating the scattering invariant Q [16] from the intensity profiles IðqÞ (see Fig. S2 in the Supplemental Material [15]), which gives an estimation of the flocculation parameter [17].…”

Interplay between Kinetics and Dynamics of Liquid-Liquid Phase Separation in a Protein Solution Revealed by Coherent X-ray Spectroscopy

“…The phase behavior of this system has been established to exhibit a lower critical solution temperature (LCST) phase behavior [25][26][27]. The kinetics of LLPS of this system has been well studied using US-AXS [25,28]. Here we aim to explore both the growth kinetics and the microscopic dynamics in order to distinguish their role in the early stage of LLPS and the domain coarsening using XPCS in the USAXS geometry.…”

“…BSA and YCl 3 were purchased from Sigma-Aldrich. Sample preparation followed our previous work [25,28]. The stock solutions of protein and salt were mixed at 21 • C with an initial protein concentration of 175 mg mL −1 and salt concentration of 42 mM.…”