Regensburg 2019 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 28: Statistical physics of biological systems II (joint session BP/DY)

BP 28.8: Vortrag

Donnerstag, 4. April 2019, 17:00–17:15, H11

Phase separation in the ensemble of fixed pH — •Omar Adame-Arana1, Christoph A. Weber1, Vasily Zavurdaev1,2, Jacques Prost3, and Frank Jülicher11Max Planck Institute for the Physics of Complex Systems, 01187 Dresden, Germany — 2Friedrich-Alexander Universität Erlangen-Nürnberg, Cauerstr. 11, 91058 Erlangen, Germany — 3Institut Curie, 26 rue d’Ulm, 75248 Paris Cedex 05, France

Recent developments at the interface of biology and physics brought to light the importance of phase separation in explaining biological processes in the cell. It has been shown that some proteins are able to phase separate in solution and form liquid-like droplets in the cytoplasm that carry out a distinct biological function. Particularly, a drop in the cytosolic pH leads to a widespread protein assembly in the cytoplasm, this phenomenon triggered our interest to the mechanism of protein phase separation as a function of pH. In order to study this mechanism, we define a model of a solution composed of macromolecules which can exist in three different charge states and have a tendency to phase separate. The pH dependence is introduced in terms of chemical reactions which control the charge state of the macromolecules. Using conservation laws and chemical equilibrium, we identify the conjugate variables of the system. We then perform a Legendre transform which defines the free energy corresponding to a fixed pH ensemble. We conclude by showing phase diagrams as a function of pH, where we find that under most conditions, phase separation is most pronounced near the isolectric point.

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