Variations of size and distribution in suspensions of sonicated phospholipid bilayers

Agarose gel partition chromatography conditions are reported which allow the separation of a range of unilaminar particles from a sonicated suspension of phosphatidyl choline. Column fractionation, radiolabeling, NMR and electron microscopy show that the unilaminar population is heterogeneous in size. The distribution is unimodal, but somewhat asymmetrical, with a broader range to larger particle diameters. The distribution is estimated to encompass vesicles differing in radius by at least 100 Å. It is also shown that populations enriched in vesicles of a chosen size range may be prepared by column fractionation methods. These results are reconciled with the previous literature on vesicle size distributions.