Stochastic dynamics of single molecules across phase boundaries
Cells need to organize their internal structure in different compartments to function properly. Recent years have seen the discovery of many biomolecular condensates that form compartments that do not require a membrane to separate them from the cytoplasm. Their formation and dynamics can be modelled by the physics of phase separation. Single-molecule experiments allow us to follow the motion of individual molecules in these condensates and across their phase boundaries. I will discuss the stochastic trajectories of single molecules in a phase-separated liquid, showing how the physics of phase coexistence affects the statistics of molecular trajectories. Starting from these results, I will investigate the thermodynamics of these individual trajectories, discuss how they can reveal the non-equilibrium nature of condensates and present how they can be used to infer key phase separation parameters. I will close by considering chemically active condensates.