Depth-profiling with giant vesicle membranes.

A phospholipid fluorescent-labeled in one of three locations was paired with a phospholipid labeled with a quencher in one of three locations within a host phospholipid bilayer. The various combinations of quenching efficiencies allowed the location of the fluorescent labels to be determined. It was found that all three labels (including one attached to the chain terminus) position themselves at the bilayer surface. The tendency of even modestly polar molecules (or sections of molecules) to gravitate to the membrane surface has numerous practical ramifications.