Fusion of fatty acid containing lecithin vesicles.

The rate and temperature at which fusion of purified homogeneous lecithin vesicles containing several per cent fatty acid occurs have been determined by analysis of proton nuclear magnetic resonance (nmr) spectra. Dimyristoyllecithin with myristic acid as 2% of the lipid was found to fuse rapidly at temperatures between 17 and 20 degrees, and dimyristoyllecithin with 4% lauric acid was found to fuse rapidly at temperatures between 11 and 15 degrees, while dimyristoyllecithin with 4% palmitic acid did not fuse at an appreciable rate anywhere in the range 17-37 degrees. These results, along with data on dipalmitoyl- and dilauroyllecithin, are discussed in terms of a possible dependence on separation of fatty acid rich phase especially conducive to fusion.