Gelation Dynamics upon Pressure-Induced Liquid–Liquid Phase Separation in a Water–Lysozyme Solution

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 nonergodicity parameter typical for gelation. We observe fast superdiffusive (γ ≥ 3/2) and slow subdiffusive (γ < 0.6) motion associated with fast viscoelastic fluctuations of the network and a slow viscous coarsening process, respectively. The dynamics age linearly with time τ ∝ t 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.

Copper drives prion protein phase separation and modulates aggregation

“…However, when adding H2O2, we observed remarkable changes in the dynamic properties of condensates (Fig. 4g): [PrP:Cu 2+ +H2O2] condensates/aggregates were characterized by super diffusive ( > 1) viscoelastic relaxation indicating network fluctuations in the condensates, likely via liquid-to-solid transition during gelation/hardening 52,53 . The loss of molecular diffusion (FRAP data, Fig.…”

Harnessing Pressure-Axis Experiments to Explore Volume Fluctuations, Conformational Substates, and Solvation of Biomolecular Systems

“…43,69,70 Recently, X-ray photon correlation spectroscopy (XPCS) was applied to study also the kinetics and dynamics of pressure-induced LLPS formation in a concentrated water− lysozyme solution (at 240 g mL −1 , 0.5 M NaCl) as a function of quench-depth into the two-phase region. 72 XPCS is a powerful tool to investigate dynamic processes at nanometer length scales and microsecond-to-second time scales in soft matter systems. The sample dynamics is reflected by the intensity fluctuations of the recorded speckle patterns of the scattered synchrotron X-ray beams.…”

“…No glass-like behavior (i.e., complete arrest) could be observed as in deep temperature-quench experiments. 72 Mukherjee et al and other groups have shown that LLPS of disordered amyloidogenic peptides, such as α-synuclein, may occur in the nucleation step of aggregation and fibril formation, which offers an alternative noncanonical aggregation pathway next to the nucleation and growth route of amyloid-forming peptides. 73 The liquid-like droplets then gradually undergo an irreversible liquid-to-solid phase transition forming amyloidlike hydrogels entrapping oligomers and fibrils.…”

“…No glass-like behavior ( i.e. , complete arrest) could be observed as in deep temperature-quench experiments …”

Coherent X-ray Scattering Reveals Nanoscale Fluctuations in Hydrated Proteins

“…XPCS has been demonstrated for a broad range of soft condensed matter systems [29,30], including amorphous water where a liquid-liquid transition was observed in the ultraviscous regime [31]. However, due to experimental difficulties in working with radiation-sensitive samples, XPCS of protein systems became possible only recently with optimized experimental procedures [32][33][34][35][36][37][38][39][40].…”