A drawback of membrane mimics deposited directly onto silicon (or other) substrates is that the bilayer is influenced by the very presence of the substrate employed to enable experimental studies. There has long been considerable interest in developing unconstrained supported membrane mimics for biophysical and biomolecular interaction studies. A number of approaches have been applied with each having their advantages and disadvantages. This work applies the ‘Floating’ Supported Bilayer (FSB) method which mimics the balance of forces seen in multilamellar vesicles to produce systems where the membrane floats on a substantial cushion of water. They are produced using sequential Langmuir-Blodgett and Langmuir-Schaeffer depositions. The first such system was the ‘double’ bilayer1 which demonstrated the necessary hydration layer, but the weak interaction between the lower layers and the substrate resulted in poor stability and limited application. A number of enhancements have subsequently been made2 3 4 with the FSB now produced on a reusable substrate with high > 96 % surface coverage regularly achieved.
This presentation will outline our work using neutron reflectometry on two fronts. Firstly from symmetric single bilayers produced from DPPC, POPC and DOPC we study the impact of the tail saturation on structural parameters of the bilayer to high precision where the area per molecule and headgroup hydration agrees well with that determined from diffraction studies of stacked bilayers under high relative humidity.5 6 Secondly I will outline our continuing work on the production of asymmetric bilayers produced with lipopolysaccharide outer membranes.7