  We study the liquid-liquid phase separation (LLPS) of a cell-free
transcription-translation (TXTL) system. When the TXTL reaction, composed of a
large amount of proteins, is concentrated, the uniformly mixed state becomes
unstable and membrane-less droplets form spontaneously. This LLPS droplet
formation can be induced when the TXTL reaction is enclosed in water-in-oil
emulsion droplets in which water evaporates (dehydration) from the surface. As
the emulsion droplets shrink, smaller LLPS droplets appear inside the emulsion
droplets and coalesce into phase-separated domains that partition the location
of proteins. We show that the LLPS in the emulsion droplets can be accelerated
by interfacial drift in the outer oil phase. This further provides an
experimental platform for studying the interplay between biological reactions
and intracellular phase separation.
