The title fluorescent probe crosses dihexadecyldimethylammonium bromide vesicular membranes l-2 orders of magnitude faster than it crosses the liposomal membranes of dipalmitoylphosphatidylcholine.
The membrane mimetic properties of simple surfactant vesicules continue to attract much attention.
1 Fundamental to the problem of chemically differentiating exovesicular and endovesicular loci of fully-functionalized, synthetic surfactant vesicles, 2.
is the competition between reaction of an added substrate at the exovesicular surface and its permeation to endovesicular reactive sites. 3 Studies have been made of the permeation of simple ions in synthetic surfactant vesicles, 4 but kinetic investigations of more complicated permeants are few.5 The useful fluorescent probe of trans-membrane transport, l-anilino-S-naphthalenesulfonate (ANS), although extensively studied in liposomal assemblies such as dipalmitoylphosphatidylcholine (DPPC),6 does not appear to have been examined with cationic vesicles, e.g., dihexadecyldimethylammonium bromide (162). We now provide initial ANS permeation results for 3 different types of 162 vesicles, and comparative data for small and large DPPC liposomes. Additionally, we describe other important properties of these molecular assemblies. Vesicle preparation. Vesicles of 162 and DPPC were prepared in pH 7.4, 0.01 M aq. imidazole buffer by (a) sonication [Braun-Sonic model 1510, immersion probe, 55-60°C, 100 W, 10 min]; (b) rapid injection (250 ul Hamilton syringe) of ethanolic surfactant into buffer