Simulation of shape transformations of lipid bilayer vesicles

Various shapes of vesicles, including sphere, prolate spheroid, oblate spheroid, and stomatocyte types, have been observed according to the osmotic difference between the inner and the outer vesicle. We investigated the process of vesicle deformation by carrying out dissipative particle dynamics simulations. With a decrease in the number of water particles in a vesicle, the transformations from sphere to prolate shape or oblate shape were observed. To investigate the mechanism of vesicle deformation in details, we carried out simulations by moving lipids between the inner and outer leaflets of the vesicle. As a result, the transforms between the prolate shape and the oblate shape could be observed. These results indicate that the shapes of vesicles are determined by the volume inside a vesicle and by the differences between the numbers of lipids forming the inner and outer leaflets of a vesicle. The result is in good agreement with the area difference elasticity model.