(575a) Controlling Vesicle Shape By Adsorption of a Semiflexible Polymer

Interactions between membranes and polymers are ubiquitous in biology, with examples including membrane-cytoskeleton interactions, the membrane-facilitated assembly of some virions, and drug delivery by polymeric carriers. Despite the importance to biology, many aspects of polymer-membrane interactions remain to be addressed, in part because the flexibility of membranes can lead to nontrivial coupling between configurations of the polymer and of the membrane. In this work, we study the adsorption of a semiflexible polymer onto a fluid membrane vesicle using Monte Carlo computer simulations. We find that polymer adsorption can induce vesicle shape changes, with configurations that depend on the polymer-membrane adsorption strength, the polymer persistence length, and the membrane bending rigidity. Stiff membranes maintain approximately spherical shapes, with the adsorbed polymer adopting configurations on the surface that are controlled by its persistence length. At smaller values of the bending rigidity, sufficiently strong adsorption of the polymer can cause invagination of the vesicle, resulting in inward budding of the membrane around a collapsed polymer or a cylindrical deformation that envelops a rod-like polymer. For small vesicles, the polymer can induce a dumbbell-like vesicle shape with a narrow membrane neck that is suggestive of protein-mediated scission mechanisms. By characterizing the shapes and statistical properties of the membrane-polymer system, we construct a pseudophase diagram that provides insight into the underlying physical interactions governing polymer adsorption onto the vesicle and the influence on vesicle shape. Analytical calculations of the energetics of idealized configurations provide additional insight into the interplay of adsorption strength, polymer persistence length, and membrane stiffness.