Gabriel N E, Roberts M F
Biochemistry. 1986 May 20;25(10):2812-21. doi: 10.1021/bi00358a012.
Stable unilamellar vesicles formed spontaneously upon mixing aqueous suspensions of long-chain phospholipid (synthetic, saturated, and naturally occurring phosphatidylcholine, phosphatidylethanolamine, and sphingomyelin) with small amounts of short-chain lecithin (fatty acid chain lengths of 6-8 carbons) have been characterized by using NMR spectroscopy, negative staining electron microscopy, differential scanning calorimetry, and Fourier transform infrared (FTIR) spectroscopy. This method of vesicle preparation can produce bilayer vesicles spanning the size range 100 to greater than 1000 A. The combination of short-chain lecithin and long-chain lecithin in its gel state at room temperature produces relatively small unilamellar vesicles, while using long-chain lecithin in its liquid-crystalline state produces large unilamellar vesicles. The length of the short-chain lecithin does not affect the size distribution of the vesicles as much as the ratio of short-chain to long-chain components. In general, additional short-chain decreases the average vesicle size. Incorporation of cholesterol can affect vesicle size, with the solubility limit of cholesterol in short-chain lecithin micelles governing any size change. If the amount of cholesterol is below the solubility limit of micellar short-chain lecithin, then the addition of cholesterol to the vesicle bilayer has no effect on the vesicle size; if more cholesterol is added, particle growth is observed. Vesicles formed with a saturated long-chain lecithin and short-chain species exhibit similar phase transition behavior and enthalpy values to small unilamellar vesicles of the pure long-chain lecithin prepared by sonication. As the size of the short-chain/long-chain vesicles decreases, the phase transition temperature decreases to temperatures observed for sonicated unilamellar vesicles. FTIR spectroscopy confirms that the incorporation of the short-chain lipid in the vesicle bilayer does not drastically alter the gauche bond conformation of the long-chain lipids (i.e., their transness in the gel state and the presence of multiple gauche bonds in the liquid-crystalline state).
将长链磷脂（合成的、饱和的以及天然存在的磷脂酰胆碱、磷脂酰乙醇胺和鞘磷脂）的水悬浮液与少量短链卵磷脂（脂肪酸链长度为6 - 8个碳）混合后，会自发形成稳定的单层囊泡。已通过核磁共振光谱、负染色电子显微镜、差示扫描量热法和傅里叶变换红外（FTIR）光谱对其进行了表征。这种囊泡制备方法可以产生大小范围为100至大于1000埃的双层囊泡。短链卵磷脂和处于室温凝胶态的长链卵磷脂组合会产生相对较小的单层囊泡，而使用处于液晶态的长链卵磷脂则会产生较大的单层囊泡。短链卵磷脂的长度对囊泡大小分布的影响不如短链与长链成分的比例大。一般来说，额外的短链会减小囊泡的平均大小。胆固醇的掺入可影响囊泡大小，短链卵磷脂胶束中胆固醇的溶解度极限决定了任何大小变化。如果胆固醇的量低于胶束状短链卵磷脂的溶解度极限，那么向囊泡双层中添加胆固醇对囊泡大小没有影响；如果添加更多胆固醇，则会观察到颗粒生长。由饱和长链卵磷脂和短链物质形成的囊泡表现出与通过超声处理制备的纯长链卵磷脂的小单层囊泡相似的相变行为和焓值。随着短链/长链囊泡尺寸减小，相变温度降低至超声处理的单层囊泡所观察到的温度。FTIR光谱证实，短链脂质掺入囊泡双层中不会大幅改变长链脂质的gauche键构象（即它们在凝胶态的反式状态以及在液晶态中多个gauche键的存在）。
