Non-equilibrium phase separation in mixtures of catalytically active particles: size dispersity and screening effects

• Published in: The European physical journal. E, Soft matter and biological physics Vol. 44; no. 9; p. 113
• Main Authors: Ouazan-Reboul, Vincent, Agudo-Canalejo, Jaime, Golestanian, Ramin
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2021; Springer Nature B.V
• Subjects: Biological and Medical Physics; Biophysics; Catalytic activity; Complex Fluids and Microfluidics; Complex Systems; Condensed matter physics; Enzymes; Equilibrium; Liquid phases; Nanotechnology; Phase diagrams; Phase separation; Physics; Physics and Astronomy; Physics of Phase Separation in Cell Biophysics: From Non-Equilibrium Droplets to Reaction-Diffusion Systems; Polymer Sciences; Reciprocity; Regular - Living Systems; Regular Article - Living Systems; Screening; Soft and Granular Matter; Substrates; Surfaces and Interfaces; Thin Films; Transient oscillations
• ISSN: 1292-8941; 1292-895X
• DOI: 10.1140/epje/s10189-021-00118-6

Biomolecular condensates in cells are often rich in catalytically active enzymes. This is particularly true in the case of the large enzymatic complexes known as metabolons, which contain different enzymes that participate in the same catalytic pathway. One possible explanation for this self-organization is the combination of the catalytic activity of the enzymes and a chemotactic response to gradients of their substrate, which leads to a substrate-mediated effective interaction between enzymes. These interactions constitute a purely non-equilibrium effect and show exotic features such as non-reciprocity. Here, we analytically study a model describing the phase separation of a mixture of such catalytically active particles. We show that a Michaelis–Menten-like dependence of the particles’ activities manifests itself as a screening of the interactions, and that a mixture of two differently sized active species can exhibit phase separation with transient oscillations. We also derive a rich stability phase diagram for a mixture of two species with both concentration-dependent activity and size dispersity. This work highlights the variety of possible phase separation behaviours in mixtures of chemically active particles, which provides an alternative pathway to the passive interactions more commonly associated with phase separation in cells. Our results highlight non-equilibrium organizing principles that can be important for biologically relevant liquid-liquid phase separation. Graphic abstract