ROLE OF THE STEREOCHEMISTRY OF THE HYDROXYL GROUP OF CHOLESTEROL AND THE FORMATION OF NONBILAYER STRUCTURES IN PHOSPHATIDYLETHANOLAMINES
ROLE OF THE STEREOCHEMISTRY OF THE HYDROXYL GROUP OF CHOLESTEROL AND THE FORMATION OF NONBILAYER STRUCTURES IN PHOSPHATIDYLETHANOLAMINES
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DOI：
10.1021/bi00448a036
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发表时间：
1989-10-31
期刊：
影响因子：
2.9
通讯作者：
EPAND, RM
中科院分区：
文献类型：
--
作者：
CHEETHAM, JJ;WACHTEL, E;EPAND, RM
通过差示扫描量热法和 X 射线衍射研究了胆固醇或表胆固醇与磷脂酰乙醇胺的混合物的相行为。通过 L.alpha 中的 X 射线衍射检测胆固醇的离散域。来自蛋黄的磷脂酰乙醇胺和合成的二油酰磷脂酰乙醇胺的相，起始摩尔分数为0.35-0.4胆固醇。在 L.alpha 中也可以检测到结晶表胆固醇的单独域。通过 X 射线衍射分析，表胆固醇的摩尔分数低至 0.16。这是表胆固醇与二反油酰磷脂酰乙醇胺的混溶性差的结果。表胆固醇不会改变 L.beta。 .fwdarw。 L.alpha。过渡或双层间距。表胆固醇对六方相圆柱体的直径也几乎没有影响。在鸡蛋磷脂酰乙醇胺和二反式磷脂酰乙醇胺中添加少量胆固醇（摩尔分数小于0.2）可促进倒六角相的形成。然而，在胆固醇摩尔分数较高的情况下，发现二油酰磷脂酰乙醇胺的液晶相稳定性显着增加，而鸡蛋磷脂酰乙醇胺则没有，这表明酰基链结构在控制这些系统中层状和非层状相的相对稳定性方面的重要性。与胆固醇相比，表胆固醇显着降低 L.alpha。 .fwdarw。低摩尔分数甾醇下的 HII 相变温度。该结果证明了添加剂的取向和运动特性在确定 L.alpha 方面的重要性。 .fwdarw。 HII 转变温度。
The phase behavior of mixtures of cholesterol or epicholesterol with phosphatidylethanolamine was studied by differential scanning calorimetry and X-ray diffraction. Discrete domains of cholesterol are detected by X-ray diffraction in the L.alpha. phase of phosphatidylethanolamine from egg yolk and synthetic dielaidoylphosphatidylethanolamine beginning at mole fractions of 0.35-0.4 cholesterol. Separate domains of crystalline epicholesterol can also be detected in the L.alpha. phase of dielaidoylphosphatidylethanolamine by X-ray diffraction at as little as 0.16 mole fraction of epicholesterol. This is a result of poor miscibility of the epicholesterol with dielaidoylphosphatidylethanolamine. Epicholesterol does not alter the L.beta. .fwdarw. L.alpha. transition or bilayer spacing. Epicholesterol also has little effect on the diameter of the cylinders of the hexagonal phase. Formation of the inverted hexagonal phase is facilitated by addition of small amounts of cholesterol (mole fraction less than 0.2) in both egg phosphatidylethanolamine and dielaidoylphosphatidylethanolamine. However, at higher mole fractions of cholesterol, the stability of the liquid-crystalline phase is found to increase markedly for dielaidoylphosphatidylethanolamine but not for egg phosphatidylethanolamine, indicating the importance of the structure of the acyl chains in controlling the relative stability of the lamellar and nonlamellar phases in these systems. In contrast to cholesterol, epicholesterol markedly lowers the L.alpha. .fwdarw. HII phase transition temperature at low mole fraction of sterol. This result demonstrates the importance of the orientation and motional properties of an additive in determining the L.alpha. .fwdarw. HII transition temperature.