ABSTRACT
Giant vesicles form spontaneously from lipid bilayers in aqueous solution. Shape transformations are also predicted to arise in vesicles consisting of a bilayer with several components due to different mechanisms. In equilibrium, vesicles will acquire the shape at which their total energy is minimal since processes such as hydrodynamic flows, convection, or transport related to temperature gradients can be neglected. The values obtained by these techniques scatter strongly. Even for the same lipid, the bending rigidity differs by a factor of 2 using different methods. Sometimes the same technique applied by different research groups yields significantly different values. The spontaneous curvature model does not contain any explicit reference to the two leaflets which form the bilayer. It had been recognized early on that there is a further energetic constraint from the fact that the two monolayers do not exchange molecules on short time scales.
