Lecture: Physics of liquid to solid transitions and microemulsions in the life of cells

26.06.2017, 15:00

Dr. Vasily Zaburdaev Max Planck Institute for the Physics of Complex Systems, Dresden

Time, place:
Monday, 26th June 2017, 15:00h
Seminar Room A2.500, MPL, Staudtstr. 2, 91058 Erlangen


Abstract:

Currently there is a constantly growing experimental evidence demonstrating the role of the physical phenomena of phase separation in the very fundamental processes inside cells. In this talk, I will give two examples of how the concepts of equilibrium physics help to understand biological systems which are intrinsically out of thermal equilibrium. First example is the liquid to solid transition. Many cells and organisms are able to survive extreme environmental conditions, where one of the most frequently occurring stresses is nutrient depletion. We could show that the protective mechanism responsible for single cell survival during nutrient depletion is the solidification of the cell cytoplasm. The lack of nutrients leads to the drop in the cytosolic pH that in turn causes widespread self-assembly of cytoplasmic proteins leading to a solid-like, mechanically stable cytoplasm. There is still a lot to understand about this and similar protective transitions occurring during heat shock or desiccation. In the second part of the talk, we will look inside of the cell nucleus. We could find a very intriguing relation between the transcriptional activity and the spatial organisation of chromatin. Remarkably, we can well understand this organisation within the framework of microemulsions. Here the separating phases are DNA and RNAs with RNA-binding proteins. The analogue of the amphiphilic compound is the actively transcribing polymerase. We could use this analogy to construct a theoretical model that fully reproduced the chromatin structure in the nucleus depending on its transcriptional activity observed in the experiments. We can now use this knowledge to better understand the impact of DNA organisation on transcriptional regulation in cells.