Continuity of Short-Time Dynamics Crossing the Liquid-Liquid Phase Separation in Charge-Tuned Protein Solutions

Area of Science:

• Biophysics
• Cell Biology
• Neuroscience

Background:

• Liquid-liquid phase separation (LLPS) drives membraneless organelle formation.
• Aberrant LLPS contributes to protein aggregation in neurodegenerative diseases.

Purpose of the Study:

• Investigate protein self-diffusion dynamics during LLPS.
• Understand the nanosecond hydrodynamic response to protein cluster formation.
• Correlate diffusion with phase splitting and temperature.

Main Methods:

• Incoherent quasi-elastic neutron spectroscopy (QENS) to probe short-time self-diffusion.
• UV-vis spectroscopy to determine local concentrations in separated phases.
• Analysis of protein samples in dissociated and phase-separated states.

Main Results:

• Short-time protein diffusion was measured across LLPS regimes.
• Local concentrations in dense and dilute phases were quantified.
• Hypothesized conserved transient protein cluster size at the transition point.

Conclusions:

• LLPS involves conserved transient protein cluster sizes during phase separation.
• Local volume fractions distinctly separate between dense and dilute phases.
• QENS provides insights into the dynamics of protein aggregation relevant to disease.