Attractive and Repulsive Interactions between Plate-like Solid Membrane Domains in Phospholipid Membranes.*

This project employed giant unilamellar phospholipid vesicles to study the interactions between solid membrane domains which act more generally as plate-like inclusions, and it made a comparison to a continuum model. The positions of multiple solid microscale membrane domains within single vesicles suggested the presence of an attractive minimum between domain pairs, short-range interdomain repulsions, and long-range inter-domain attractions. We quantified the range of the potential minimum in vesicles containing only two domains, reporting features of a true pair potential. As previous work has only reported repulsive interactions or attractive interactions individually, our discovery of a distinct minima translates to preferred domain positioning. These interactions result from the shear elasticity of the solid domains, which tend to expel Gaussian curvature into the fluid membrane phase, generically competes with the global spherical topology of the vesicle. We also discovered the ability to toggle interactions, and shift the targeted positioning, by osmotic adjustment or mechanical manipulation of the fluid membrane by employing micropipettes or osmotic pressure.