Surface Phase Transitions with Membrane Binding

Protein-rich condensates in living cells can wet the cell membrane and surfaces of membrane-bound organelles. In cells, proteins are also known to bind to membranes leading to a molecular layer of bound molecules. It is not clear how binding affects the physics of surface phase transitions such as wetting and prewetting. Here, we derive the corresponding continuum theory for a three-dimensional bulk in the presence of a two-dimensional membrane. We find that membrane binding gives rise to multiple prewetting transitions and a shifted wetting transition line. Strikingly, the coupling between membrane and bulk can shift the prewetting line far away from binodal which facilitates prewetting already at very low bulk concentrations. Our work suggests that the physics of surface phase transitions combined with molecular binding can play an important role to control the formation of protein-rich phases at intra-cellular surfaces.