INCORPORATION OF N-ACYLETHANOLAMINE PHOSPHOLIPIDS INTO EGG PHOSPHATIDYLCHOLINE VESICLES - CHARACTERIZATION AND PERMEABILITY PROPERTIES OF THE BINARY-SYSTEMS

We have studied the effect of the N-acylphosphatidylethanolamine (N-ac ylPE) on the permeability properties of liposomes composed primarily o f egg phosphatidylcholine using a fluorescent anionic dye, carboxyfluo rescein, as model solute. Leakage from liposomes decreased and vesicle size increased with increasing N-acylPE content. In addition, measure ment of the trapped aqueous space, using the same dye marker, showed a correlation between trapped volume and vesicle size determined by dyn amic light scattering. Permeability parameters were calculated accordi ng to the pseudo-first-order analysis. It appears that N-acylPE stabil izes liposomes at least in part through its ability to impart surface negative charge, in accord with the results obtained with potassium ch loride as encapsulated solute. These results agreed well with osmotic response of anionic lipid vesicles. Cholesterol stabilizes N-acylPE li posomes in a proportional manner to the molar fraction of the effector .