Dynamic sorting of lipids and proteins in cellular membranes plays a critical role in establishing and maintaining distinct compositions in various organelles. Recent experiments found that the lipid sorting in a membrane tube highly depends on the pulling speed at the tip. However, the mechanism of this velocity dependence has not yet been revealed. In this Letter, we found that when a membrane is deformed rapidly, the lipid flow induced by fast membrane shape change will significantly affect the sorting results. The competition between the curvature-driven lipid sorting and the pulling-induced lipid flow leads to novel behaviors. When a membrane tube is pulled out from a liquid ordered ($L_o$) domain at a constant speed, slow pulling leads to the formation of a liquid disordered ($L_d$) tube, while fast pulling results in a $L_o$ tube. Interestingly, in a membrane tube pulled at an intermediate speed, alternate $L_d$ and $L_o$ domains appear in the tube. The sorting dynamics and the corresponding pulling force were systematically studied. The results of this study could lead to a better understanding of the dynamic sorting and traffic of lipids and proteins in living cells.

• Received 18 June 2012

DOI:https://doi.org/10.1103/PhysRevLett.109.198101