PHASE-BEHAVIOR AND BILAYER PROPERTIES OF FATTY-ACIDS - HYDRATED 1-1 ACID SOAPS
PHASE-BEHAVIOR AND BILAYER PROPERTIES OF FATTY-ACIDS - HYDRATED 1-1 ACID SOAPS
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DOI：
10.1021/bi00358a011
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发表时间：
1986-05-20
期刊：
影响因子：
2.9
通讯作者：
SMALL, DM
中科院分区：
文献类型：
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作者：
CISTOLA, DP;ATKINSON, D;SMALL, DM
由脂肪酸和具有饱和（10-18个碳）和ω-的钾皂形成的一系列1：1酸-皂化合物在水中的物理性质本文用差示扫描量热法（DSC）、X射线衍射、直接光显微镜和偏光显微镜研究了9个单不饱和（18个碳）烃链。DSC示出了对应于结晶水的熔化、结晶脂质烃链的熔化以及1：1酸-皂化合物分解成其母体脂肪酸和皂的三个相变。低角和广角X-射线衍射图案显示对应于酸皂晶体，六方II型液晶和层状液晶的间距（随着水合作用的增加）。层状相从双层重复距离68（在45%H2O下）膨胀到303埃。(at 90% H2O）。直接和偏振光显微照片表明形成髓鞘数字以及双折射光学纹理对应的六方和层状中间相。假设1：1的油酸氢钾和水为两个组分，我们绘制了温度-组成相图。使用吉布斯相律对数据的解释表明，在> 30%的水时，烃链熔融伴随着1：1的酸-皂化合物的分解，并且系统从两组分变为三组分系统。水合1：1脂肪酸/皂系统与水合皂系统的比较表明，极性基团之间电荷排斥程度的降低导致半电离脂肪酸在过量水中形成双层而不是胶束。1：1脂肪酸/皂系统提供了对游离脂肪酸在体内运输和代谢期间形成的物理状态的深入了解，因为在pH 7.4下，水和磷脂双层中的脂肪酸接近半电离。
The physical properties in water of a series of 1:1 acid-soap compounds formed from fatty acids and potassium soaps with saturated (10-18 carbons) and .omega.-9 monounsaturated (18 carbons) hydrocarbon chains have been studied by using differential scanning calorimetry (DSC), X-ray diffraction, and direct and polarized light microscopy. DSC showed three phase transitions corresponding to the melting of crystalline water, the melting of crystalline lipid hydrocarbon chains, and the decomposition of the 1:1 acid-soap compound into its parent fatty acid and soap. Low- and wide-angle X-ray diffraction patterns revealed spacings that corresponded (with increasing hydration) to acid-soap crystals, hexagonal type II liquid crystals, and lamellar liquid crystals. The lamellar phase swelled from bilayer repeat distances of 68 (at 45% H2O) to 303 .ANG. (at 90% H2O). Direct and polarized light micrographs demonstrated the formation of myelin figures as well as birefringent optical textures corresponding to hexagonal and lamellar mesophases. Assuming that 1:1 potassium hydrogen dioleate and water were two components, we constructed a temperature-composition phase diagram. Interpretation of the data using the Gibbs phase rule showed that, at > 30% water, hydrocarbon chain melting was accompanied by decomposition of the 1:1 acid-soap compound and the system changed from a two-component to a three-component system. Comparison of hydrated 1:1 fatty acid/soap systems with hydrated soap systems suggests that the reduced degree of charge repulsion beween polar groups causes half-ionized fatty acids in excess water to form bilayers rather than micelles. The 1:1 fatty acid/soap system provides insights into the physical states formed by free fatty acids during transport and metabolism in vivo since, at pH 7.4, fatty acids in water and in phospholipid bilayers are near half-ionization.