Prewetting Drives Membrane Curvature

When polymer mixtures interact with membranes, wetting and prewetting transitions occur leading to distinct surface phases. Previous work from our group studied the thermodynamics of these surface phases and showed that near membrane criticality, pre-wetting transitions are greatly enhanced. This past work considered flat inextensible membranes, but in many cases prewet domains seem to play roles in curving and shaping the membrane. Here we seek to understand how prewet domains can generate mechanical stresses on membranes. We use the formalism of the lateral pressure profile which allows us to understand how these stresses lead to changes in the effective parameters governing membrane shape. We construct a minimal landau theory, and from the free energy functional we calculate the lateral pressure profile of the membrane-polymer system. We then study the membrane morphology by using this profile to predict curvature. To test our theory, we develop a Monte Carlo simulation on a 3D lattice composed of tethers, polymers, and a 2D Ising membrane with curvature. By combining theory and simulation, we show how curvature influences prewetting phase stability. Our work is useful in understanding morphology and biological functions, such as postsynaptic densities, nanotubular structures, and endocytic or exocytic buds, which are believed to be regulated by polymer droplets and membrane interactions.