Structural changes in membranes of large unilamellar vesicles after binding of sodium cholate.
Structural changes in membranes of large unilamellar vesicles after binding of sodium cholate.
复制标题
胆酸钠结合后大单层囊泡膜的结构变化。
作者：
R. Schubert;K. Beyer;H. Wolburg;K. Schmidt
研究了胆盐胆酸盐与单层囊泡的相互作用。在低胆酸盐含量，蛋黄卵磷脂膜的平衡结合测量表明，胆酸盐结合到外部囊泡小叶。在增加的浓度下，阻碍了胆盐与膜的进一步结合。在膜溶解开始之前，二苯基己三烯荧光各向异性降低到最小值。然后增加到膜增溶的胆酸盐浓度范围内的初始值。在更高的胆酸盐浓度下，荧光各向异性的下降表明混合盘胶束转化为球形胶束。在结合胆酸盐/卵磷脂的摩尔比超过0.15的囊泡膜的扰动导致从囊泡内空间的寡糖的瞬时释放。诱导释放所需的胆酸盐浓度取决于截留糖的大小。胆固醇稳定膜，而尽管膜的顺序增强，鞘磷脂不稳定的膜对胆酸盐。冷冻断裂电子显微镜和磷-31核磁共振（31 P NMR）也反映了膜结构的变化，在最大胆酸结合的囊泡。在~（31）P核磁共振谱中，叠加在磷脂双分子层中典型的各向异性谱线上，发现了一个各向同性的峰，这个信号很可能是由于加入胆酸盐后形成了更小的囊泡。结果进行了讨论，在肝细胞中的胆盐/膜相互作用。它的结论是，囊泡胆盐运输在细胞质中是不可能的，胆酸盐结合仅限于外小叶的小管部分的质膜。
The interaction of the bile salt cholate with unilamellar vesicles was studied. At low cholate content, equilibrium binding measurements with egg yolk lecithin membranes suggest that cholate binds to the outer vesicle leaflet. At increasing concentrations, further bile salt binding to the membrane is hampered. Before the onset of membrane solubilization, diphenylhexatriene fluorescence anisotropy decreases to a shallow minimum. It then increases to the initial value in the cholate concentration range of membrane solubilization. At still higher cholate concentrations, a drop in fluorescence anisotropy indicates the transformation of mixed disk micelles into spherical micelles. Perturbation of the vesicle membranes at molar ratios of bound cholate/lecithin exceeding 0.15 leads to a transient release of oligosaccharides from intravesicular space. The cholate concentrations required to induce the release depend on the size of the entrapped sugars. Cholesterol stabilizes the membrane, whereas, in spite of enhanced membrane order, sphingomyelin destabilizes the membrane against cholate. Freeze-fracture electron microscopy and phosphorus-31 nuclear magnetic resonance (31P NMR) also reflect a change in membrane structure at maximal cholate binding to the vesicles. In 31P NMR spectra, superimposed on the anisotropic line typically found in phospholipid bilayers, an isotropic peak was found. This signal is most probably due to the formation of smaller vesicles after addition of cholate. The results were discussed with respect to bile salt/membrane interactions in the liver cell. It is concluded that vesicular bile salt transport in the cytoplasm is unlikely and that cholate binding is restricted to the outer leaflet of the canalicular part of the plasma membrane.
胆盐/卵磷脂混合胶束的结构二态性。
影响因子：
2.9
作者：
Müller,K
通讯作者：
Müller,K