Chemical Engineering Seminar

Phase separation is generally a thermodynamic process in which a mixture reaches its lowest free energy state by self-assembling into meso- (or macro-) scale regions that are concentrated or dilute in a given molecular component. A rapidly growing body of experiments suggests that phase separation is responsible for the formation of membraneless domains (also known as biomolecular condensates, with length scales of the order of microns) in biological cells, which have important biological functions. I will first focus upon recent observations of phase separation of chromatin in the nucleus and show that a new paradigm is emerging in which the genetic material is not necessarily uniformly distributed within the nucleus but separated into domains which in some cases, have a complex, "marshland", mesoscale structure. But while many of the equilibrium aspects can be at least semi-quantitatively understood by extensions of statistical physics, biological molecules often do not have constant overall compositions as is the case in the examples of equilibrium phase separation; for example, over time, the cell produces and degrades many proteins. The recent understanding of such strongly non-equilibrium effects has informed the theoretical physics of phase separation and results in new predictions for the size, shape and fluctuations of domains in cellular phase separation.

* Collaborations: Omar Adame Arana, Gaurav Bajpai, Dan Deviri, Amit Kumar (Dept. Chemical and Biological Physics), group of Emmanuel Levy (Dept. Structural Biology) and group of Talila Volk (Dept. Molecular Genetics)