Pseudocritical Behavior and Unbinding of Phospholipid Bilayers

The temperature dependence of the small-angle neutron scattering from fully hydrated multilamellar phospholipid bilayers near the main phase transition is analyzed by means of a simple geometric model which yields both the lamellar repeat distance as well as the hydrophobic thickness of the bilayer and the interlamellar aqueous spacing. The results for two different lipids show that the lamellar repeat distance displays pseudocritical behavior with a value of the exponent that is in accordance with the theory for critical unbinding transitions of interacting membranes.