We have succeeded in determining the mechanical properties of a non-lamellar lipid phase, the inverted hexagonal form thought to correspond to transient structures during membrane fusion. It appears that different combinations of lipids have different most-favored or """"""""intrinsic"""""""" radii of curvature. The work of forced deviations from ths configuration can be described in terms of a bending modulus whose value is nearly the same for all lipids. It also seems that in these non-lamellar forms the hydrocarbon chains are under little strain but rather act to fill space. Hydrocarbons added to bilayers will tend to drive the lipids to non lamellar forms. These lines of physical reasoning lead immediately to better understanding of the reasons for the biochemical metabolic steps in lipid metabolism. It also provides a strong indication for a morphological role for hydrocarbons such as dolichol known for its biochemical function anchoring oligosaccharides during synthesis. We have further pursued the problem of relating the mechanical motion of neighboring membranes or linear macromolecules to the long-range forces acting between them. We have used a measure of extent of molecular motion from the widths of x-ray diffraction peaks scattering from arrays of condensed DNA together with direct force measurements to see how forces and motion affect each other.
