Alamethicin-mediated fusion of lecithin vesicles.

It was recently shown that alamethicin greatly facilitates the fusion of small, sonicated, lecithin bilayer vesicles. In the present work the details of this fusion process have been followed by monitoring the inner and outer choline methyl signals separately by proton magnetic resonance spectroscopy. It is shown that during the alamethicine-induced fusion some of the antibiotic molecules become translocated from the extravesicular aqueous medium into the enclosed intravesicular space, and these alamethicine molecules were found to affect the choline methyl signals from the inner half of the bilayer only. No evidence was obtained for transmembrane coupling of the two halves of the bilayer in the presence of alamethicin or for any effects that might be construed as due to incorporation of alamethicin molecules into the hydrophobic core of the bilayer.