QUANTITATIVE-ANALYSIS OF HOLES IN SUPPORTED BILAYERS PROVIDING THE ADSORPTION ENERGY OF SURFACTANTS ON SOLID SUBSTRATE

We investigated the topography of mixed bilayers consisting of a first monolayer of DMPE (dimyristoylphosphatidylethanolamine) and of a seco nd monolayer of DOPC (dioleoylphosphatidylcholine) that were Langmuir- Blodgett deposited on mica. Using transfer ratio measurements and tapp ing mode atomic force microscopy experiments, we show that the subnano metric holes in the bilayers result from the desorption of lipids of t he first monolayer during the transfer of the second monolayer. We pre sent a new simple technique based on the quantitative analysis of thes e holes that allows determination of the adsorption energy of amphiphi lic molecules on solid surfaces. This technique is valid for relativel y low adsorption energies in the range 1 to 10 k(B)T.