How Curvature and Tension Direct Morphology and Interactions of Solid Membrane Domains in Fluid Vesicles

Multi-phospholipid giant unilamellar vesicles containing at least one high melting lipid (such as DPPC) exhibit the coexistence of fluid and solid membrane domains. To the extent that the inner and outer leaflets of the membrane are matched in composition and molecular number, symmetry dictates flat solid domains. The curvature imposed we show that at sufficiently high tensions, the curvature imposed by global vesicle shape influences the growth of solid domains, producing deviations from hexagon domain shape to include edge instabilities that appear as flowers. At high tensions domains appear to fracture. At lower tensions, exclusion of curvature into the fluid membrane region produces reversible interactions between solid domains that give rise to aggregation or long range order, depending on the relative sizes of vesicle domains, curvature, and excess membrane area. These behaviors are demonstrated in a model experimental vesicle system.