Evidence of the hydration force in gel phase lipid multibilayers

¹ Atomic Energy of Canada Limited - Chalk River, Ontario, K0J 1J0, Canada
² Department of Physics, University of Guelph - Guelph, Ontario, N1G 2W1, Canada

Received: 5 November 1996
Accepted: 20 February 1997

Abstract

We present applied osmotic pressure vs. distance curves constructed from high-resolution neutron and X-ray diffraction scattering density profiles of dipalmitoyl phosphatidylcholine (DPPC) multibilayers in the gel phase. The data, obtained from three distinct regions of the lipid bilayer, show that at small interbilayer distances the repulsion observed in these bilayers can be accounted for by the so-called “hydration force”. Also, a previous observation of a sharp upward break in the pressure-distance curve of highly ordered DPPC bilayers is not the result of steric repulsion but rather of a 2D 3D phase transition. The data are consistent with a recent theoretical model which predicts that the repulsive forces in ordered phases (e.g., and phases) are dominated by the hydration force.