Comment on "Theory for the bending anisotropy of lipid membranes and tubule formation" - art. no. 013901

We point out that the mechanism proposed by Chen [Phys. Rev. E 59, 619', (1 999)] for the stabilization of tubular vesicles via bending anisotropy and edge tension cannot be applied to symmetric bilayers. Other possible mechan isms are reviewed, with special emphasis on one involving a nematic order o f the surfactant polar heads.