McCabe P J, Green C
Chem Phys Lipids. 1977 Dec;20(4):319-30. doi: 10.1016/0009-3084(77)90072-x.
Of the polar lipids studied (phospholipids and glycolipids), only phosphatidylcholine and sphingomyelin can disperse in water with up to 2 mol cholesterol/mol polar lipid. However, mixtures of phosphatidylethanolamine with small amounts of phosphatidylcholine and mixed lipids from mitochondria and myelin will also form sterol-rich dispersions. Steroids in which the 3beta-OH group is replaced by an oxo function do not form such steroid-rich dispersions. Electron microscopy and optical rotatory dispersion (ORD) show that sterols disperse with cerebrosides and gangliosides to form cylindrical structures with the regions around C atoms 3 and 7 of the sterol in less polar environments than those they occupy in phospholipid liposomes. It is proposed that choline-containing phospholipids facilitate entry of sterol molecules into the outer leaflet of cell surface membranes but that the phospholipid composition itself will not give rise to an asymmetric distribution of sterol in membranes with a high cholesterol content.
在所研究的极性脂质（磷脂和糖脂）中，只有磷脂酰胆碱和鞘磷脂能够在每摩尔极性脂质含有多达2摩尔胆固醇的情况下分散于水中。然而，磷脂酰乙醇胺与少量磷脂酰胆碱的混合物以及来自线粒体和髓磷脂的混合脂质也会形成富含甾醇的分散体。3β-羟基被氧代官能团取代的类固醇不会形成这种富含类固醇的分散体。电子显微镜和旋光色散（ORD）表明，甾醇与脑苷脂和神经节苷脂分散在一起，形成圆柱形结构，甾醇中碳原子3和7周围的区域所处的极性环境比它们在磷脂脂质体中所处的极性环境更小。有人提出，含胆碱的磷脂有助于甾醇分子进入细胞表面膜的外层小叶，但磷脂组成本身不会导致甾醇在高胆固醇含量的膜中不对称分布。
