Andrew P. Shreve, Michael C. Howland, Annapoorna R. Sapuri-Butti, Toby W. Allen and Atul N. Parikh Langmuir 24, 13250-13253 (Letter) 2008

The asymmetric distribution of charged molecules between the leaflets of solid-substrate-supported phospholipid bilayers is studied using imaging ellipsometry, fluorescence microscopy, and numerical solutions of the Poisson−Boltzmann equation. Experiments are facilitated by the use of patterned substrates that allow for side-by-side comparison of lipid monolayers and supported bilayers. On silica surfaces, negatively charged lipid components are shown to be enriched in the outer leaflet of a supported bilayer system at modest salt concentrations. The approaches developed provide a general means for determining asymmetries of charged components in supported lipid bilayers.