Membrane domains are widely hypothesized to directly influence a variety of biological processes from viral entry into cells to cellular signaling and exocytosis. Many such processes involve coupling of an outer leaflet stimulus to inner leaflet reactions, as in immune signaling, but the mechanism of this coupling is experimentally undetermined. In model membrane systems such as giant unilamellar vesicles, liquid domains are easily imaged by fluorescence microscopy and are in registry with each other across the symmetric bilayer. The work in this proposal aims to understand how lipid domains interact and couple to each other, in both symmetric model bilayers, and asymmetric model bilayers which more closely mimic the composition of the plasma membrane. By introducing alkanes in between the two leaflets of a planar Montal-Mueller bilayer, land varying the temperature and electrical field, exquisite control over the bilayer and alkane layer thickness will be achieved. In this way, specific hypotheses of the mechanism by which the two leaflets interact will be tested. [unreadable] [unreadable] [unreadable]