Regensburg 2025 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 12: Biomaterials, Biopolymers and Bioinspired Functional Materials I (joint session CPP/BP)

CPP 12.2: Talk

Monday, March 17, 2025, 17:15–17:30, H46

How specific binding induces sol-gel transitions and liquid-liquid phase separation in RNA/protein solutions: Coarse-grained simulations versus Semenov-Rubinstein Theory — •Xinxiang Chen, Jude Ann Vishnu, Pol Besenius, Julian König, and Friederike Schmid — Johannes Gutenberg-University, Mainz, Germany

Liquid-liquid phase separation plays a central role in cellular organization, including RNA splicing. RNA-protein interactions are crucial to these processes. A key factor in controlling the phase behavior of RNA-protein systems is the sequence of binding and neutral domains. Using molecular dynamics simulations, we investigate phase transitions in RNA-protein solutions that are driven solely by specific binding interactions. The model omits nonspecific interactions including electrostatic interactions. We show that specific binding interactions induce a percolation transition with double reentrant behavior without phase separation, if the neutral linker size is long. Comparing our results with the two-component Rubinstein-Semenov theory, we find that the theory qualitatively reproduces the phase diagram of the percolation transition and the impact of the neutral domains. Phase separation is observed when reducing the neutral linker size in an asymmetric system, resulting in a closed-loop phase diagram. We also study the effect of modulating the sequence and find that blockiness of sticker sites introduces microstructure in the dense liquid phase. These insights enhance our understanding of how specific binding and domain arrangement regulates condensate formation in RNA-protein systems.

Keywords: Sol-gel transition; Liquid-liquid phase separation; RNA; Protein; Molecular dynamics simulation