The effect of freeze-thawing on the size of egg yolk phosphatidylcholine (EggPC) vesicles in the presence of 0—40 mol% distearoylphosphatidylethanolamine-polyethylene glycol 2000 (DSPE-PEG) was studied. Mean diameters of the vesicles fell into a range of 80—150 nm after 10 times freeze-thawing in spite of their original size. In the process of freeze-thawing, two opponent events, one is fission and the other is fusion, occurred at the same time. DSPE-PEG accelerated the fusion event.
