Felgner P L, Freire E, Barenholz Y, Thompson T E
Biochemistry. 1981 Apr 14;20(8):2168-72. doi: 10.1021/bi00511a015.
Results are presented which demonstrate that purified trisialoganglioside spontaneously incorporates into performed phospholipid vesicles. Determinations of the extent of incorporation were made by separating large unilamellar dipalmitoylphosphatidylcholine vesicles containing incorporated ganglioside from micellar ganglioside on a Sepharose-2B column. Incorporation occurs without appreciably altering the vesicular character of the phospholipid bilayer as judged by the maintenance of an outside/inside ratio, determined by 31P NMR, comparable to that of the original vesicles. All of the incorporated ganglioside ias accessible to neuraminidase, indicating that incorporation occurs only on the outer face of the bilayer. The thermotropic behavior of these asymmetric dipalmitoylphosphatidylcholine-trisialoganglioside vesicles, examined by high sensitivity scanning calorimetry, strongly suggests that the incorporated ganglioside is intercalated into the outer monolayer of the vesicle bilayer. Calorimetric studies indicate that the ganglioside stabilizes these vesicular structures by inhibiting the fusion of small vesicles that occurs below the phase-transition temperature. These structures are a representative model system, which like the mammalian plasma membrane contain an asymmetric distribution of glycosphingolipid in the outer surface.
结果表明，纯化的三唾液酸神经节苷脂能自发地掺入预先形成的磷脂囊泡中。通过在Sepharose - 2B柱上分离含有掺入神经节苷脂的大单层二棕榈酰磷脂酰胆碱囊泡与胶束状神经节苷脂，来测定掺入程度。通过31P NMR测定的外部/内部比率维持在与原始囊泡相当的水平，由此判断，掺入过程并未明显改变磷脂双层的囊泡特性。所有掺入的神经节苷脂都可被神经氨酸酶作用，这表明掺入仅发生在双层膜的外表面。通过高灵敏度扫描量热法检测这些不对称的二棕榈酰磷脂酰胆碱 - 三唾液酸神经节苷脂囊泡的热致行为，有力地表明掺入的神经节苷脂插入到了囊泡双层的外单层中。量热研究表明，神经节苷脂通过抑制在相变温度以下发生的小囊泡融合来稳定这些囊泡结构。这些结构是一个典型的模型系统，类似于哺乳动物的质膜，在外表面含有糖鞘脂的不对称分布。
