Adhesion in egg lecithin multilayer systems produced by cooling

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Abstract
Slightly hydrated egg lecithin was aligned mostly parallel to the glass plates of the sample cells by squeezing it to a thickness of 20 μm. The rest of the cell was filled with water and the lipid was left to swell at elevated temperatures to bilayer mean spacings between 3 and 17 nm. Cooling by a few °C gave rise to induced adhesion in the semicylindrical border (and myelin cylinders) where the mean spacing was larger than in the bulk. From the contact roundings of membranes adhering to stacks of other membranes we obtained the lateral tension (dyn cm-1) inducing the adhesion as a function of the equilibrium mean spacing. An extensive analysis of the data in terms of van der Waals attraction and undulatory repulsion leads to serious contradictions. They suggest the intervention of a new, submicroscopic roughness of unstressed lecithin membranes absorbing plenty of membrane area