A 2D-ELDOR study of the liquid ordered phase in multilamellar vesicle membranes
A 2D-ELDOR study of the liquid ordered phase in multilamellar vesicle membranes
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DOI：
10.1016/s0006-3495(03)75067-x
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发表时间：
2003-04-01
影响因子：
3.4
通讯作者：
Freed, JH
中科院分区：
文献类型：
--
作者：
Costa, AJ;Shimoyama, Y;Freed, JH
2D-ELDOR光谱已被用来研究的动态结构的液体有序（Lo）相与液晶（Lc）相的多层磷脂囊泡没有（Lc）和（Lo）胆固醇，使用末端链和头基标记和自旋标记的胆甾烷。在大多数情况下，发现这两个阶段的光谱是显着不同的。因此，2D-ELDOR光谱的目视检查提供了区分膜中两相的方便方法。详细的分析表明，这些观测结果是由于增加了在Lo阶段的有序性和修改的重取向率。在Lo相中，酰基链经历比在Lc相中更快的旋转扩散和更高的有序性，而自旋标记的胆甾烷表现出更慢的旋转扩散和更高的有序性。另一方面，胆碱，头基在Lo阶段表现出更快的运动和减少，但重新排列的顺序与Lc阶段。在胆固醇的存在下，在Lo相中的微观平移扩散速率显著降低。这些结果与以前的研究进行了比较，并提供了一个一致的模型来解释他们在动态结构的差异的Lo和Lc阶段。
2D-ELDOR spectroscopy has been employed to study the dynamic structure of the liquid-ordered (Lo) phase versus that of the liquid-crystalline (Lc) phase in multibilayer phospholipid vesicles without (Lc) and with (Lo) cholesterol, using end-chain and headgroup labels and spin-labeled cholestane. The spectra are in most cases found to be dramatically different for these two phases. Thus, visual inspection of the 2D-ELDOR spectra provides a convenient way to distinguish the two phases in membranes. Detailed analysis shows these observations are due to increased ordering in the Lo phase and modified reorientation rates. In the Lo phase, acyl chains undergo a faster rotational diffusion and higher ordering than in the Lc phase, whereas spin-labeled cholestane exhibits slower rotational diffusion and higher ordering. On the other hand, the choline, headgroup in the Lo phase exhibits faster motion and reduced but realigned ordering versus the Lc phase. The microscopic translational diffusion rates in the Lo phase are significantly reduced in the presence of cholesterol. These results are compared with previous studies, and a consistent model is provided for interpreting them in terms of the differences in the dynamic structure of the Lo and Lc phases.