Abstract

Liquid-liquid phase separation (LLPS) and subsequent liquid-to-solid transition is implicated in membraneless organelles formation as well as disease associated protein aggregation. However, how liquid-to-solid transition is initiated inside a liquid droplet remains unclear. Here, using studies at single droplet resolution, we show that liquid-to-solid transition of -synuclein (-Syn) liquid droplets is associated with significant changes in the local microenvironment as well as secondary structure of the protein, which is prominently observed at the center of the liquid droplets. With the ageing of liquid droplets, the "structured" core at the center gradually expands and propagates over entire droplets. Further, during droplet fusion, smaller, homogeneous droplets progressively dissolve and supply proteins to the larger, heterogeneous droplets containing solid-like core at their center. The present study will significantly help to understand the physical mechanism of LLPS and liquid-to-solid transition in biological compartmentalization as well as in protein aggregation associated with human neurodegenerative disorders. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/465113v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@2a3406org.highwire.dtl.DTLVardef@bd8148org.highwire.dtl.DTLVardef@172b4eaorg.highwire.dtl.DTLVardef@1c3965f_HPS_FORMAT_FIGEXP M_FIG C_FIG