Budding dynamics of multicomponent tubular vesicles.

Real-time budding dynamics of multicomponent, tubular lipid vesicles was investigated. By using a fluorescence microscope, three typical growth modes of the buds were observed, corresponding, respectively, to bud growth through coalescence between flat patches, a bud and a patch, as well as that of two buds. The spatial and temporal scales measured in the observation were used to estimate the bending rigidity of the membrane. In the late stage, the continuing coalescence between the buds resulted in large shape deformation of the vesicles, from tubular to spherical vesicles, and the number of the buds decayed with time as N approximately t-2/3. This scaling relation was observed for the first time in experiment and confirmed early theoretical predictions. Our observation showed a difference between the diffusivity of the buds on the lipid membrane and that of the embedded membrane proteins.