THERMOTROPIC PROPERTIES OF PHOSPHATIDYLETHANOLS

Phosphatidylethanol is formed when ethanol substitutes in the transpho sphatidylation reaction catalyzed by phospholipase D. The structural a nd thermotropic properties of dipalmitoylphosphatidylethanol and dimyr istoylphosphatidylethanol have been studied using differential scannin g calorimetry, fluorescence spectroscopy, and P-31 nuclear magnetic re sonance, These lipids exist in a bilayer phase with no indication of n onbilayer phase formation, as shown by P-31 nuclear magnetic resonance , It was found that the phase behavior of these phospholipids before a nd during the main chain melting transition is different in 50 mM Tn's buffer compared to salt solutions. The phase transition behavior and the 6-propionyl-2-(dimethylamino)naphthalene (Prodan) fluorescence spe ctra for both lipids are consistent with the formation of the interdig itated gel phase under certain conditions, Both lipids become interdig itated in Tris-HCl, and ethanol enhances the formation of this phase. Comparative studies of the 6-propionyl-2-(dimethylamino)naphthalene sp ectra in dipalmitoylphosphatidylglycerol, dielaidoylphosphatidylethano lamine, and dipalmitoyiphosphatidylcholine further elucidate the value and limitations of this probe as a diagnostic tool for lipid structur e.