The division of vesicles requires the fission of closed membrane necks but does not require active processes

Abstract

One important objective of soft matter science and synthetic biology is to construct synthetic systems and processes that mimic the division of cells and organelles. Such division processes have been achieved experimentally for giant vesicles and in-silico for nanovesicles. Here, we analyze recent studies of these division processes, focussing on results that have been obtained by our group, using a combination of theory, experiment, and simulation. We show that the division of vesicles requires the formation and fission of closed membrane necks but does not require chemomechanical coupling to active processes such as nucleotide hydrolysis. Closed membrane necks are formed when the vesicle volume is decreased or the membrane area is increased, provided the vesicle is enclosed by an asymmetric bilayer with a sufficiently large transbilayer asymmetry between its two leaflets. The membrane necks experience a constriction force that is controlled by the spontaneous curvature for giant vesicles and by the stress asymmetry for nanovesicles. A sufficiently large constriction force leads to neck fission and vesicle division as observed for vesicle membranes (i) with uniform lipid-protein composition, (ii) with intramembrane domains of distinct lipid-protein compositions, and (iii) in contact with condensate droplets. Most of these biomimetic division processes involve membrane proteins that act to increase the transbilayer asymmetry but none of them is coupled to an active process such as nucleotide hydrolysis.