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lipid membrane; vesicle; azobenzene; photoswitch; molecular dynamics;
Abstract:
Biomembranes are constantly remodeled and in cells, these processes are controlled and modulated by an assortment of membrane proteins. Here, we show that such remodeling can also be induced by photo-responsive molecules. We demonstrate the morphological control of giant vesicles in the presence of a water-soluble orthotetrafluoroazobenzene photoswitch (F-azo) and show that the shape transformations are based on an increase in membrane area and generation of spontaneous curvature. The vesicles exhibit budding and the buds can be retracted by using light of a different wavelength. In the presence of F-azo, the membrane area can increase by more than 5% as assessed from vesicle electrodeformation. To elucidate the underlying molecular mechanism and the partitioning of F-azo in the membrane, we used molecular dynamics simulations. Comparison with theoretically calculated shapes reveals that the area difference between the two leaflets of the vesicle membrane is not constrained during the budding process and that the experimentally 2 observed shapes are well described by the spontaneous curvature model. Our results show that exo- and endocytotic events can be controlled by light and that these photo-induced processes provide an attractive method to change membrane area and morphology.