Fluid phase connectivity in an isomorphous, two-component, two-phase phosphatidylcholine bilayer.

Two-dimensional fluid phase connectivity is examined in mixed bilayers of dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine as a function of composition and temperature at constant pressure using fluorescence recovery after photobleaching (FRAP). These isomorphous phospholipid mixtures exhibit nearly ideal mixing behavior. Dilauroyl phosphatidylethanolamine covalently linked through its amino function to NBD is used as the fluorescent probe in this study. These studies show the line of connectivity to be coincident with the line connecting the midpoints of all tie lines in the two-phase region of the phase diagram.