Fission of the bilayer lipid tube

The fusion of two black lipid membranes results in the formation of peculiar bilayer lipid tubes ('cylindrical') membranes (Neher, E. (1974) Biochim. Biophys. Acta 373, 328-336 and Melikyan, G.B., Abidor, L.G., Chernomordik, L.V. and Chailakhyan, L.M. (1983) Biochim. Biophys. Acta 730, 395-398). The mechanical stability of such tubes has been investigated experimentally and theoretically. With increasing hydrostatic pressure on the outside of the tube the radius of its middle part decreases. After this radius has reached a critical value, which constitutes 0.55 of the radius of the tube base, there occurs a collapse of the tube and its disintegration into two planar bilayers (fission). Expressions are obtained which relate the transmembrane difference of the hydrostatic pressure, causing the collapse, to the geometrical characteristics of the tube (its length and the radius of its base) and to the tension of the lipid bilayer. A method for measuring the membrane tension is proposed on the basis of the phenomenon considered.