Continuity of\nShort-Time Dynamics Crossing the Liquid–Liquid\nPhase Separation in Charge-Tuned Protein Solutions

Liquid–liquid phase separation (LLPS) constitutes\na crucial\nphenomenon in biological self-organization, not only intervening in\nthe formation of membraneless organelles but also triggering pathological\nprotein aggregation, which is a hallmark in neurodegenerative diseases.\nEmploying incoherent quasi-elastic neutron spectroscopy (QENS), we\nexamine the short-time self-diffusion of a model protein undergoing\nLLPS as a function of phase splitting and temperature to access information\non the nanosecond hydrodynamic response to the cluster formation both\nwithin and outside the LLPS regime. We investigate the samples as\nthey dissociate into microdroplets of a dense protein phase dispersed\nin a dilute phase as well as the separated dense and dilute phases\nobtained from centrifugation. By interpreting the QENS results in\nterms of the local concentrations in the two phases determined by\nUV–vis spectroscopy, we hypothesize that the short-time transient\nprotein cluster size distribution is conserved at the transition point\nwhile the local volume fractions separate.