Solid-state NMR methods to investigate biomolecular condensates, protein phase transition, phase separation and coacervates.
The formation of biomolecular condensates has been linked to a broad range of essential cellular processes, including immune signaling cascades, mRNA transport, and autophagy. Conversely, phase-separated condensates have also been associated with aberrant protein misfolding and subsequent aggregation in neurodegenerative disease-related processes. Protein phase separation and phase transitions involve the formation of heterogeneous and dynamic assemblies that can evolve into gel-like or semi-crystalline states, which are challenging to characterize using high-resolution structural biology techniques. Solid-state nuclear magnetic resonance (NMR) spectroscopy now offers a broad arsenal of methods to probe the structural and dynamic features of viscous condensates, elastic solids, coacervates and rigid protein assemblies. This review provides an overview of solid-state NMR approaches that are readily applicable and discusses potential methodological developments to investigate protein condensates and coacervates as well as to study protein phase separation and phase transitions.