The second studied permeation enhancer was oleic acid. Oleic acid is known to work by a rather different mechanism than ethanol. Instead of irreversibly damaging liposomes, it incorporates itself into the membrane structure, slightly disrupts the ordered packing of the phospholipids, and makes the membrane more permeable to all molecules . Even though the measured permeation was very slow (CF release occurred over 10 hours), permeability still increased from a limiting value close to zero to 6.3 ‧ 10 -10 cm/s (Fig. ). The two permeation enhancement experiments demonstrate the ability of the liposomal assay to capture the effect of additional chemical species on the permeation rate of the fluorescent probe.