Departamento de Bioquímica y Biología Molecular "A", Facultad de Veterinaria, Regional Campus of International Excellence Mare Nostrum , Universidad de Murcia , Apartado de Correos 4021 , E-30080 Murcia , Spain.
Langmuir. 2018 Mar 13;34(10):3336-3348. doi: 10.1021/acs.langmuir.7b04142. Epub 2018 Feb 28.
α-Tocopherol is considered to carry on a very important role as an antioxidant for membranes and lipoproteins and other biological roles as membrane stabilizers and bioactive lipids. Given its essential role, it is very important to fully understand its location in the membrane. In this work, the vertical location of vitamin E in saturated membranes has been studied using biophysical techniques. Small- and wide-angle X-ray diffraction experiments show that α-tocopherol alters the water layer between bilayers in both 1,2-dimyristoyl- sn-glycero-3-phosphocholine (DMPC) and 1,2-dipalmitoyl- sn-glycero-3-phosphocholine (DPPC), indicating its proximity to this surface. The quenching of the intrinsic fluorescence of α-tocopherol indicates a low quenching efficiency by acrylamide and a higher quenching by 5-doxyl-PC than by 9- and 16-doxyl-PC. These results suggest that in both DMPC and DPPC membranes, the chromanol ring is not far away from the surface of the membrane but within the bilayer. H nuclear Overhauser enhancement spectroscopy magic-angle spinning-nuclear magnetic resonance studies showed that α-tocopherol is localized in a similar manner in DMPC and DPPC membranes, with the chromanol ring embedded in the upper part of the hydrophobic bilayer. Using attenuated total reflection-Fourier transform infrared spectroscopy, it was observed that the tail chain of α-tocopherol lies nearly parallel to the acyl chains of DMPC and DPPC. Taking these results together, it was concluded that in both DMPC and DPPC, the hydroxyl group of the chromanol ring will establish hydrogen bonding with water on the membrane surface, and the main axis of the α-tocopherol molecule will be perpendicular to the bilayer plane.
生育酚被认为在膜和脂蛋白等生物中作为抗氧化剂以及作为膜稳定剂和生物活性脂质发挥着非常重要的作用。考虑到其重要作用，充分了解其在膜中的位置非常重要。在这项工作中，使用生物物理技术研究了维生素 E 在饱和膜中的垂直位置。小角和广角 X 射线衍射实验表明，生育酚改变了 1,2-二肉豆蔻酰基-sn-甘油-3-磷酸胆碱（DMPC）和 1,2-二月桂酰基-sn-甘油-3-磷酸胆碱（DPPC）双层之间的水层，表明其接近该表面。生育酚的固有荧光猝灭表明丙烯酰胺的猝灭效率较低，而 5-二氧芐基-PC 的猝灭效率高于 9-和 16-二氧芐基-PC。这些结果表明，在 DMPC 和 DPPC 膜中，色满环离膜表面不远，而是在双层内。H 核 Overhauser 增强魔角旋转核磁共振研究表明，生育酚在 DMPC 和 DPPC 膜中以相似的方式定位，色满环嵌入疏水区双层的上部。使用衰减全反射-傅里叶变换红外光谱法观察到生育酚的尾部链几乎平行于 DMPC 和 DPPC 的酰基链。综合这些结果可以得出结论，在 DMPC 和 DPPC 中，色满环的羟基将与膜表面的水形成氢键，生育酚分子的主轴将垂直于双层平面。
