Curvature-driven lipid sorting in a membrane tubule

Motivated by recent experiments that implicate the mechanical properties of membranes in lipid sorting, we examine the interplay of lipid composition and curvature in membrane tubules. We study how the coupling between membrane composition and membrane bending stiffness and tension affects tubule formation. Drawing a tubule from a vesicle leads to a rearrangement of composition in which the phase of higher flexibility segregates into the highly curved tubule. For point forcing, the force vs extension curve can have a sharp drop just as the tubule begins to form.