Physical laws to control and regulate composition of multi-component biomolecular condensates

Abstract Biomolecular phase separation is a fundamental process in biology which facilitates many biological functions. Through the process of phase separation, cells can compartmentalize certain molecules into a highly- concentrated condensed phase – commonly termed a condensate, or membraneless organelle (MLO) – that is distinct from the surrounding environment. These MLOs are important to biology because they are functionally distinct from their membrane-bound counterparts, and can be regulated by external stimuli, sometimes forming or dissociating spontaneously upon a change in conditions in the surroundings. Usually, MLOs are stabilized by a small subset of molecules, such as multivalent proteins containing intrinsically disordered regions, but contain dozens to hundreds of other proteins, nucleic acids, and other molecules. It is important to understand the physics and molecular interactions that determine the relative composition, and how this relates to the function and efficiency of an MLO. This is especially important for development of novel drugs that target proteins and nucleic acids within disease-causing condensates in biology. I plan to develop my research program to tackle important problems in this field by developing theoretical models to describe interactions and phase separation of multi-component mixtures of proteins and other biomolecules. Successful completion of this work will enable researchers to make predictions of how biomolecules contribute to phase separation in a multi-component system. We will also work to understand how MLOs are regulated by cellular conditions such as temperature, pH, or concentration of salt and other small molecules. We particularly wish to focus on the question of how phase separation is controlled by the presence of small molecules, such as metabolites, or pharmaceutical drugs. By working with theoretical and computational methods, we can consistently model the interactions of small molecules with MLO constituents, and how they partition inside a condensate. Successful completion of this work will contribute greatly to the community's understanding of how condensates are regulated and provide important design principles for small molecule, and biologic drugs developed specifically to target MLOs.