Individual leaflet phase effect on nanometer-scale surface properties of phospholipid bilayers.

Phospholipid bilayers were formed on mica using Langmuir-Blodgett technique and liposome fusion, as a model system for biomembranes. Nanometer-scale surface physical properties were quantitatively characterized upon the different phases of the monolayers. The less hydration/steric forces were observed at the liquid-phase of the lipid layer than at the solid-phase. The forces appear to be related to the low mechanical stability of the lipid layer. The force changed more significantly at the outer-lipid-layer-transition than at the inner-lipid-layer-phase-transitions. In addition, it was found that the stability also depended on the asymmetry of the lipid bilayers. For the lipid bilayers which were composed of liquid-phase and solid-phase monolayers, the more hydration/steric forces were shown over the bilayers whose inner lipid layer was in liquid-phase than in solid-phase.