Aliphatic chain transitions of phospholipid vesicles and phospholipid dispersions determined by polarization of fluoroscence

The polarization of fluorescence of dansyl phosphatidylethanolamine and 9-methylanthracene shows that these compounds are reliable indicators of the order-disorder transitions of the phospholipid aliphatic chains in bilayer systems. The transition is better defined in phospholipid dispersion than in vesicles. It is concluded that the two models are not identical as far as the structure near the melting temperature is concerned. Experiments in turbid solutions were performed with horizontal slits either in the incident or emitted beams, which eliminate the effect of light scattering. This improvement in experimental technique may facilitate the fluorescence polarization study of membrane suspensions.