(473e) Polysaccharides Pattern the Phase Behavior of Lipid Membranes

Hydrated networks of glycans (polysaccharides) in the form of cell walls, periplasms or gel-like matrices are ubiquitously present adjacent to cellular plasma membranes. Yet despite their abundance, the function of glycans in the extracellular milieu is largely unknown. Here we show that glycans as part of hydrated networks can interact directly with lipids in model membranes. Because of this interaction, the spatial configuration of the glycans controls the phase behaviour of multiphase lipid membranes: inhomogeneous glycan networks stabilize large lipid domains at the characteristic length scale of the network, while homogeneous glycan networks suppress macroscopic lipid phase separation. We find that glycans pattern lipid phase separation due to a preference for ordered lipid phases, and that the patterning is thermally reversible, which is an indication that the effect is not kinetic but rather is thermodynamic. The discovery here that glycan networks can control the length scale of domains in adjacent lipid membranes necessarily has implications for plasma membrane mediated transport processes and potentially rationalizes some long-standing puzzling observations that differentiate the behaviour of native plasma membranes and model membranes. Our results may also indicate a more intimate coupling between cellular lipidomes and glycomes than realized currently.