| Abstract
| - Shape transformations and topological changes of lipid vesicles, such as fusion, budding, and fission, haveimportant chemical physical and biological significance. In this paper, we study the fission process of lipidvesicles. Two distinct routes are considered that are both based on an asymmetry of the lipid distributionwithin the membrane. This asymmetry consists of a nonuniform distribution of two types of lipids. In thefirst mechanism, the two types of lipids are equally distributed over both leaflets of the membrane. Phaseseparation of the lipids within both leaflets, however, results in the formation of rafts, which form buds thatcan split off. In the second mechanism, the asymmetry consists of a difference in composition between thetwo monolayers of the membrane. This difference in composition yields a spontaneous curvature, reshapingthe vesicle into a dumbbell such that it can split. Both pathways are studied with molecular dynamics simulationsusing a coarse-grained lipid model. For each of the pathways, the conditions required to obtain completefission are investigated, and it is shown that for the second pathway, much smaller differences between thelipids are needed to obtain fission than for the first pathway. Furthermore, the lipid composition of the resultingsplit vesicles is shown to be completely different for both pathways, and essential differences between thefission pathway and the pathway of the inverse process, i.e., fusion, are shown to exist.
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