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BP: Fachverband Biologische Physik

BP 53: Complex Fluids and Soft Matter (joint BP/DY/CPP)

BP 53.8: Vortrag

Freitag, 20. März 2015, 11:30–11:45, H 1058

How to regulate droplet position in a heterogeneous chemical environment? — •Samuel Krüger^{1, 2}, Christoph Weber¹, Jens-Uwe Sommer^{2, 3}, and Frank Jülicher¹ — ¹Max Planck Institute for the Physics of Complex Systems, Dresden — ²Leibniz Institute of Polymer Research Dresden e.V., Dresden — ³Technische Universität Dresden, Institute of Theoretical Physics, Dresden, Germany

P granules are droplet-like structures consisting of RNA and proteins. They occur in Caenorhabditis elegans embryo and are known to determine its germ lineage. Interestingly, P granules are segregated to one side of the cell. There is evidence that the droplet position is regulated by a spatially inhomogeneous protein called Mex-5. Here we propose a model that simplifies the multicomponent nature of the cytoplasm as a ternary mixture: The P granule material, the background fluid, and a regulator mimicking Mex-5. Using our model we aim to understand the physical principles controlling the droplet position. To this end we consider lattice-based Monte Carlo simulations for a ternary mixture, where the microscopic interactions between the components are captured by three Flory-Huggins parameters. Considering a linear regulator gradient we observe two stationary states. Droplets localise in regions of lowest regulator concentration if the regulator exhibits a high affinity to the solvent, and vice versa. We present evidence that the transition between the localisation at highest and lowest regulator concentration can be regarded as a phase transition. Beyond biology, understanding how the droplet positions can be regulated offers the possibility to design switchable units for chemical computing.