Protein interactions in liquid-liquid phase separation

Increasing experimental evidence indicates the structures in cellular processes.1,2 The droplet state of proteins, which is formed by liquid-liquid phase separation is a fundamental state, along with the native and amyloid states.3 The lack of highresolution structural data is a major bottleneck to elucidate the biophysical forces, which drive formation of the droplet state. We know that protein condensates violate many classical rules of molecular recognition, owing to their variable compositions and heterogeneous conformations.4 The interactions within condensates are weakly specific, which are modulated by the cellular conditions (location, tions, co-expression partners, etc.) leading to context-dependent assembly/disassembly.5 In addition, droplets may irreversibly maturate into the amyloid state, which is often driven by familial mutations.6 This issue focuses on understanding those interactions, which underlie the versatile cellular cusses the interaction network of phase separated proteins and find that it is distinct from the rest of changes in material state, which can partly explain