STUDIES ON PHOSPHATIDYLCHOLINE VESICLES . FORMATION AND PHYSICAL CHARACTERISTICS

A method is described for the separation of phosphatidylcholine vesicles, formed by prolonged ultrasonic irradiation under nitrogen in 0.1 M buffered NaCl solution, by molecular sieve chromatography on large-pore agarose gels. One fraction of the separated vesicles was found to be homogeneous by the criteria of gel filtration, sedimentation velocity ultracentrifu-gation, and electron microscopy. Experimental data which support the homogeneous vesicle as a shelllike structure, about 250 A in diameter, with a continuous phosphatidylcholine bilayer surrounding a volume of solvent are presented. The following physical parameters were established for the homogeneous vesicles: s20,w, 2.1 S; D20,w, 1.87 × 10-7cm2sec-1; ̅v, 0.9885 ml g-1; [η], 0.041 dl g-1; and vesicle weight, 2.1 × 106. © 1969, American Chemical Society. All rights reserved.