Liposome Perparation. Individual lipid or its mixture with DOPE in the desired mole ratio was dissolved in autoclaved Wheaton glass vials. Thin films were made by evaporation of the organic solvent under a steady stream of dry nitrogen. Last traces of organic solvent were removed by keeping these films under vacuum overnight. Freshly autoclaved water (Malli-Q) was added to an individual film such that final concentration of the cationic lipid was 0.5 mM. The mixtures were kept for hydration at 4 ํc for 10-12 h and were repeatedly freeze-thawed (ice-cold water to 70 ํc) with