Electrolyte effects on bilayer tubule formation by a diacetylenic phospholipid

A general effect by dissolved electrolytes to destabilize the curvature of bilayer tubules prepared from the diacetylenic phospholipid, 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine is not found. This observation discounts the role of an electrostatic interaction between polarization charges on the edges of a ferroelectric bilayer as a means by which the cylindrical curvature may be stabilized in these structures (de Gennes, P. G. 1987. C. R. Acad. Sci. Paris. 304:259-263). The solution-mediated ionic interactions of electrolytes with this phospholipid appear not to influence significantly the relative stability of the crystalline state of the tubule, but at high levels of a few salts, may affect the nucleation and growth of the crystalline bilayer. Curvature of the bilayer in these tubular structures apparently derives from an interaction that is not very sensitive to the presence of electrolytes. Cylindrical curvature may alternatively arise from a bending force within the bilayer that is intrinsic to the anisotropic packing of the lipid molecules (Helfrich, W., and J. Prost. 1988. Phys. Rev. A38:3065-3068; Chappell, J. S., and P. Yager. 1991. Chem. Phys. Lipids. In press), and may therefore be largely determined by the packing interactions within the hydrophobic region of the tubular bilayer.