Yaroslavov A A, Melik-Nubarov N S, Kabanov V A, Ermakov Y A, Azov V A, Menger F M
Polymer Department, School of Chemistry, Lomonosov Moscow State University, Russia.
Chemistry. 2001 Nov 19;7(22):4835-43. doi: 10.1002/1521-3765(20011119)7:22<4835::aid-chem4835>3.0.co;2-y.
Laser microelectrophoresis (coupled with conductance, fluorescence, and dynamic light scattering) is shown to be a highly instructive tool in comparing the dynamics of conventional and gemini surfactants embedded within vesicle bilayers. The following can be listed among the more important observations and conclusions: a) Cationic conventional surfactant, added to a "solid" (gel) lipid vesicle containing an anionic phospholipid, charge-neutralizes only half the anionic charge. With a "liquid" (liquid crystalline) vesicle, however, the entire negative charge is neutralized. Thus, the cationic conventional surfactant can "flip-flop" readily only in the liquid membrane. b) A cationic gemini surfactant charge-neutralizes only the anionic lipid in the outer membrane leaflet of either solid or liquid membranes, thus indicating an inability to flip-flop regardless of the phase-state of the bilayer. c) Mixed population experiments show that surfactants can hop from one vesicle to another in liquid but not solid membranes. d) In liquid, but not solid, bilayers, a surface-adsorbed cationic polymer can electrostatically "drag" anionic surfactant from the inner leaflet to the outer leaflet where the polymer resides. e) Peripheral fluorescence quenching experiments show that a cationic polymer, adhered to anionic vesicles, can be forced to dissociate in the presence of high concentrations of salt or an anionic polymer. f) Adsorbed polymer, of opposite charge to that imparted to vesicles by a gemini surfactant, is unable to dislocate surfactant even in a liquid membrane. g) In our systems, ionic polymers will not bind to neutral vesicles made solely of zwitterionic phospholipid. On the other hand, ionic polymers bind to neutral vesicles if charge neutrality is obtained by virtue of the membrane containing equimolar amounts of cationic and anionic surfactant. This is attributable to surfactant segregation within the bilayer. h) Experiments prove that polymer migration can occur among a population of neutral ternary vesicles.
激光微电泳（结合电导、荧光和动态光散射）被证明是比较嵌入囊泡双层中的传统表面活性剂和双子表面活性剂动力学的极具启发性的工具。以下是一些更重要的观察结果和结论：a）添加到含有阴离子磷脂的“固体”（凝胶）脂质囊泡中的阳离子传统表面活性剂仅中和一半的阴离子电荷。然而，对于“液体”（液晶）囊泡，全部负电荷被中和。因此，阳离子传统表面活性剂仅能在液体膜中容易地“翻转”。b）阳离子双子表面活性剂仅中和固体或液体膜外层膜小叶中的阴离子脂质，因此表明无论双层的相态如何都无法翻转。c）混合群体实验表明，表面活性剂可以在液体而非固体膜中从一个囊泡跳跃到另一个囊泡。d）在液体而非固体双层中，表面吸附的阳离子聚合物可以通过静电作用将阴离子表面活性剂从内膜小叶“拖”到聚合物所在的外膜小叶。e）周边荧光猝灭实验表明，附着在阴离子囊泡上的阳离子聚合物在高浓度盐或阴离子聚合物存在下会被迫解离。f）与双子表面活性剂赋予囊泡的电荷相反的吸附聚合物即使在液体膜中也无法使表面活性剂移位。g）在我们的系统中，离子聚合物不会与仅由两性离子磷脂制成的中性囊泡结合。另一方面，如果通过膜中含有等摩尔量的阳离子和阴离子表面活性剂来实现电荷中性，则离子聚合物会与中性囊泡结合。这归因于双层内表面活性剂的分离。h）实验证明聚合物迁移可以在一群中性三元囊泡中发生。
