Crucial Role of the Double Bond Isomerism in the Steroid B-Ring on the Membrane Properties of Sterols. Grazing Incidence X-Ray Diffraction and Brewster Angle Microscopy Studies
Crucial Role of the Double Bond Isomerism in the Steroid B-Ring on the Membrane Properties of Sterols. Grazing Incidence X-Ray Diffraction and Brewster Angle Microscopy Studies
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DOI：
10.1021/acs.langmuir.5b00896
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发表时间：
2015-07-07
期刊：
影响因子：
3.9
通讯作者：
Fontaine, Philippe
中科院分区：
文献类型：
--
作者：
Flasinski, Michal;Wydro, Pawel;Fontaine, Philippe
三种胆固醇前体-去氨甾醇，酶甾醇和羊毛甾醇-在空气/水界面形成的单层中进行了全面表征。该研究基于表面压力(pi)-面积(A)等温线的配准，并辅以应用现代物理化学技术：掠射x射线衍射（GDCD）和布鲁斯特角度显微镜（BAM）进行的原位分析。在这种方法中，我们对胆固醇生物合成途径中所研究的甾醇的分子结构与其膜性质之间的相关性感兴趣。我们的研究结果表明，只有去氨甾醇在朗缪尔单分子层中的表现与胆固醇相当，后者的分子在单分子层中排列成六角形晶格，而剩下的两种甾醇具有截然不同的性质。我们发现，酶甾醇和羊毛甾醇分子在水面上以二维斜细胞的形式组织，尽管它们的方向垂直于单层平面。对所研究的甾醇的化学结构进行比较，得出的结论是，造成这种不寻常行为的唯一结构动机是B甾醇环上的双键，它位于去氨甾醇中与其他两种甾醇中不同的位置。这个在科学文献中被忽视的问题似乎对生物膜中的甾醇活性具有至关重要的意义。我们发现，甾醇分子的这种结构修饰是它们在生物膜中适应正常功能的直接原因。
Three cholesterol precursors-desmosterol, zymesterol, and lanosterol-were comprehensively characterized in monolayers formed at the air/water interface. The studies were based On registration of the surface pressure (pi)-area (A) isotherms complemented with in situ analysis performed with application of modern physicochemical techniques: grazing incidence X-ray diffraction (GDCD) and Brewster angle microscopy (BAM). In this approach we were interested in the correlation between molecular structures of the studied sterols found in the cholesterol biosynthetic pathway and their membrane properties. Out results revealed that only desmosterol behaves in Langmuir monolayers comparably to cholesterol, the molecules of which arrange in the monolayers into a hexagonal lattice, while the two remaining sterols possess extremely different properties. We found that molecules of both zymosterol and lanosterol are organized on the water surface in the two-dimensional oblique unit cells despite the fact that they are oriented perpendicular to the monolayer plane: The comparison of chemical structures of the investigated sterols leads to the conclusion that the only structural motive that can be responsible for such unusual behavior is the double bond in the B sterol ring, which is located in desmosterol in a different position from in the other two sterols. This issue, which was neglected in the scientific literature, seems to have crucial importance for sterol activity in biomembranes. We showed that this structural modification in sterol molecules is directly responsible for their adaptation to proper functioning in biomembranes.