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BP: Fachverband Biologische Physik

BP 20: Poster IIIa

BP 20.26: Poster

Mittwoch, 20. März 2024, 11:00–14:30, Poster B

Mean-filed theory for fibrillar aggregation and nematic-isotropic phase separation — •Kafa Alameh^{1, 2} and Christoph Weber¹ — ¹Mesoscopic Physics of Life, Institute of Physics, Universitätsstr. 1, Augsburg, Germany — ²Center for Systems Biology Dresden, Pfotenhauerstr. 108, 01307 Dresden, Germany

Cells use droplet-like compartments to spatially organize their interior into sub-compartments, known as membrane-less organelles. Such organelles are liquid condensates and provide distinct physical environments for chemical processes. Recently, it has been shown that various proteins with beta-sheet structures, such as FUS, are involved in protein aggregation diseases such as ALS and Alzheimer's. Moreover, FUS-rich condensates were shown to undergo aberrant "phase transition," leading to fibrillar, solid-like aggregates. Several theoretical studies have focused on how phase-separated compartments affect the irreversible aggregation of dilute monomers; however, the interplay between aggregation and phase separation at non-dilute conditions remains elusive. Such conditions are particularly relevant at the condensate interface, where aggregates are often nucleated and enriched. Here, we propose a mean-field theory accounting for the interplay between aggregation, condensate formation, and phase transition at condensate interfaces. We find a rich phase behavior; three coexisting phases differing in density and the degree of order: disordered-dilute, disordered-dense, and nematic-dense phases. Our theory suggests the possibility of finding ordered membrane-less organelles in regulatory pathways of neurodegenerative diseases.

Keywords: liquid liquid phase separation; aggregation; nematic liquid crystals; condensates; solid