Experimental and theoretical study of toroidal vesicles

We report the observation of toroidal and higher genus vesicles of diacetylenic phospholipids, a class of polymerizable amphiphiles. When unpolymerized, the vesicles exhibit different toroidal shapes in quantitative agreement with recent theoretical predictions. When partially polymerized, only a specific family of shapes has been observed: the Clifford torus or the branch of nonaxisymmetric shapes obtained by its conformal transformations. Assuming that partially polymerized vesicles are permeable on short time scale, we give a physical explanation of our findings. We also report the results of a variational calculation which approximates the nonaxisymmetric shape problem for finite spontaneous curvature.