A fluid floating bilayer

¹ Institut Laue-Langevin - B.P. 156, F-38042 Grenoble Cedex, France
² INFM - Genova, Italy
³ Institut Charles Sadron (CNRS-UPR 22.) - 6 rue Boussingault, F-67083 Strasbourg Cedex, France
⁴ Spectrométrie Physique (CNRS-UMR 5588, Université Grenoble I.) - B.P. 87, F-38402 St Martin d'Hères Cedex, France
⁵ Bergische Universität Wuppertal, Fachbereich Physik - D-42097 Wuppertal, Germany
⁶ DRFMC/SP2M/SGX CEA - 17 Avenue des Martyrs, F-38054 Grenoble, France

Corresponding author: graner@ujf-grenoble.fr

Received: 13 January 2000
Accepted: 20 October 2000

Abstract

A highly hydrated lipid bilayer, floating a few Åabove another one adsorbed on a smooth solid substrate, was prepared at room temperature where lipids (DSPC) are in gel phase, then heated at several temperatures including the pretransitional temperature and the chain melting temperature . A precise in situ characterization by neutron reflectivity led to two new results. First, even when in fluid phase the floating bilayer was structured and stable; it thus provides a flexible model system for physical and biophysical studies of membranes. Second, at intermediate temperatures, a spectacular maximum in both inter-bilayer distance and bilayer roughness was simultaneously observed. It might be a direct observation of the balance between energy minimization and entropic repulsion, leading to an estimation of the dimensionless parameter , where A is the Hamacker constant and κ the bending modulus.