Phase behavior and crystalline structures of cholesteryl ester mixtures: a C-13 MASNMR study.
Phase behavior and crystalline structures of cholesteryl ester mixtures: a C-13 MASNMR study.
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胆固醇酯混合物的相行为和晶体结构：C-13 MASNMR 研究。
DOI：
10.1016/s0006-3495(95)80420-0
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Hamilton,JA
中科院分区：
文献类型：
--
作者：
Guo,W;Hamilton,JA
胆固醇酯是胆固醇在正常生理中的转运和储存形式，但也是动脉粥样硬化斑块中的重要脂质。为了更好地了解胆固醇酯在组织和斑块中的分子性质，我们研究了纯的和混合的胆固醇酯的多晶型和介晶型特征的固态C-13 NMR魔角样品旋转（MASNMR）。研究了两个单组分（胆甾醇亚油酸酯（CL，C18：2）和胆甾醇亚麻酸酯（CLL，C18：3））、四个二元体系（胆甾醇棕榈酸酯（CP，C16：0）与CL、CLL或胆甾醇油酸酯（CO，C18：1）和CO/CL）、一个三元体系（CO/CP/CL）和一个四元体系（CO/CP/CL/CLL）的温度依赖性。混合比例基于从喂食胆固醇的新西兰白色兔解剖的动脉粥样硬化斑块的组成。C-13 MASNMR确定了相变温度，确定了所有系统中存在的相，并提供了有关分子结构的新信息。例如，固体CL表现出具有多种分子构象的无序结构，而纯CLL具有与三种最常见的表征形式（MLII、MLI、BL）不同的晶体结构。在二元混合物中，每种胆固醇酯的晶体结构由其自身的特征共振确定。结果表明，CP总是以其天然的BL形式存在，但CL和CO受混合物组成的影响。CL诱导形成MLII晶体的共存CP（55重量%）。当CO从各向同性相冷却时，它作为MLII和无定形形式的混合物存在。CP的存在显著加速了无定形形式向MLII形式的转化。对于从氯仿共干燥的三元混合物，CL与CO共结晶的MLII形式和CP存在的BL形式。少量CLL的加入略微增加了固体混合物的不均匀性，但对晶体结构或相变影响不大。C-13 MASNMR代表了反映生物样品组成的胆固醇酯混合物的物理表征的有力方法。
Cholesteryl esters are a transport and storage form of cholesterol in normal physiology but also a significant lipid in atherosclerotic plaques. To understand better the molecular properties of cholesteryl esters in tissues and plaques, we have studied the polymorphic and mesomorphic features of pure and mixed cholesteryl esters by solid state C-13 NMR with magic angle sample spinning (MASNMR). The temperature-dependent properties of two single components (cholesteryl linoleate (CL, C18:2) and cholesteryl linolenate (CLL, C18:3)), four binary systems (cholesteryl palmitate (CP, C16:0) with CL, CLL or cholesteryl oleate (CO, C18:1), and CO/CL), one ternary system (CO/CP/CL), and one quaternary system (CO/CP/CL/CLL) were studied. The mixing ratios were based on the composition of an atherosclerosis plaque dissected from a cholesterol-fed New Zealand white rabbit. C-13 MASNMR determined the phase transition temperatures, identified the phases present in all systems, and provided novel information about molecular structures. For example, solid CL exhibited a disordered structure with multiple molecular conformations, whereas pure CLL had a crystalline structure different from the three most commonly characterized forms (MLII, MLI, BL). In binary mixtures, the crystalline structure of each cholesteryl ester species was identified by its own characteristic resonances. It was found that CP always existed in its native BL form, but CL and CO were influenced by the composition of the mixture. CL was induced to form MLII crystals by the coexisting CP (55 wt%). When CO was cooled from the isotropic phase, it existed as a mixture of MLII and an amorphous form. The presence of CP significantly accelerated the conversion of the amorphous form to the MLII form. For the ternary mixture co-dried from chloroform, CL cocrystallized with CO in the MLII form and CP existed in BL form. Addition of a small amount of CLL slightly increased the heterogeneity of the solid mixture, but had little effect on the crystal structures or the phase transitions. C-13 MASNMR represents a powerful method for physical characterization of cholesteryl ester mixtures reflecting the composition of biological samples.