Vinson P K, Talmon Y, Walter A
Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis 55455.
Biophys J. 1989 Oct;56(4):669-81. doi: 10.1016/S0006-3495(89)82714-6.
Vesicle-micelle transition structures of egg phosphatidylcholine (PC) and octyl glucoside (OG) mixtures were observed in the vitrified hydrated state by cryo-transmission electron microscopy (cryo-TEM) and correlated with the macroscopic and molecular changes previously associated with micellization monitored by 90 degrees light scattering and resonance energy transfer between fluorescent lipid probes. Several distinct structural changes occurred as OG was added to the PC vesicles. First, the average vesicle size decreased from 160 nm to less than 66 nm with no apparent change or decrease in optical density (OD). Then, associated with a small rise in OD, samples with open vesicles were observed coexisting with pieces of lamellae and long cylindrical micelles; more micelles were seen at higher [OG]. This mixture of vesicles and cylindrical micelles occurred in the region of the phase diagram previously attributed to vesicle opening, and possibly vesicle size increase. At higher [OG], small spheroidal micelles coexisting with cylindrical micelles correlated with a decrease in OD and changes in the fluorescence signal. At high [OG] when the solution appeared clear, spheroidal micelles were the dominant structure. By using cryo-TEM, a technique which preserves the original microstructure of fluid systems and provides direct images at 1 nm resolution, we have elucidated the vesicle-micelle transition and identified intermediates not known previously in the PC/OG system.
通过冷冻透射电子显微镜（cryo-TEM）在玻璃化水合状态下观察了鸡蛋磷脂酰胆碱（PC）和辛基葡糖苷（OG）混合物的囊泡-胶束转变结构，并将其与先前通过90度光散射和荧光脂质探针之间的共振能量转移监测的与胶束化相关的宏观和分子变化相关联。向PC囊泡中添加OG时发生了几种明显的结构变化。首先，平均囊泡尺寸从160 nm减小到小于66 nm，而光密度（OD）没有明显变化或降低。然后，伴随着OD的小幅上升，观察到具有开放囊泡的样品与薄片和长圆柱形胶束碎片共存；在较高的[OG]下可以看到更多的胶束。这种囊泡和圆柱形胶束的混合物出现在相图中先前归因于囊泡开放以及可能的囊泡尺寸增加的区域。在较高的[OG]下，与圆柱形胶束共存的小球形胶束与OD的降低和荧光信号的变化相关。在高[OG]时，当溶液看起来清澈时，球形胶束是主要结构。通过使用冷冻透射电子显微镜，这是一种保留流体系统原始微观结构并以1 nm分辨率提供直接图像的技术，我们阐明了囊泡-胶束转变并鉴定了PC/OG系统中以前未知的中间体。
