Department of Physics and Astronomy, Calvin University, Grand Rapids, Michigan 49546-4403, United States.
Department of Physics, IUPUI, Indianapolis, Indiana 46202-3273, United States.
Langmuir. 2020 May 12;36(18):4908-4916. doi: 10.1021/acs.langmuir.0c00176. Epub 2020 Apr 30.
Vitamin E (α-tocopherol) and a range of other biological compounds have long been known to promote the H (inverted hexagonal) phase in lipids. Now, it has been well established that purely hydrophobic lipids such as dodecane promote the H phase by relieving extensive packing stress. They do so by residing deep within the hydrocarbon core. However, we argue from X-ray diffraction data obtained with 1-palmitoyl-2-oleoylphosphatidylcholine (POPE) and 1,2-dioleoylphosphatidylcholine (DOPE) that α-tocopherol promotes the H phase by a different mechanism. The OH group on the chromanol moiety of α-tocopherol anchors it near the aqueous interface. This restriction combined with the relatively short length of α-tocopherol (as compared to DOPE and POPE) means that α-tocopherol promotes the H phase by relieving compressive packing stress. This observation offers new insight into the nature of packing stress and lipid biophysics. With the deeper understanding of packing stress offered by our results, we also explore the role that molecular structure plays in the primary function of vitamin E, which is to prevent the oxidation of polyunsaturated membrane lipids.
维生素 E（α-生育酚）和一系列其他生物化合物长期以来一直被认为可以促进脂质中的 H（反六方）相。现在已经确定，像十二烷这样纯粹的疏水脂质通过缓解广泛的堆积压力来促进 H 相。它们通过位于烃核深处来实现这一点。然而，我们根据用 1-棕榈酰基-2-油酰基磷脂酰胆碱（POPE）和 1,2-二油酰基磷脂酰胆碱（DOPE）获得的 X 射线衍射数据得出结论，α-生育酚通过不同的机制促进 H 相。α-生育酚色满醇部分上的 OH 基团将其锚定在水相界面附近。这种限制加上 α-生育酚相对较短的长度（与 DOPE 和 POPE 相比）意味着 α-生育酚通过缓解压缩堆积压力来促进 H 相。这一观察结果为包装压力的性质和脂质生物物理学提供了新的见解。通过我们的结果提供的对包装压力的更深入了解，我们还探讨了分子结构在维生素 E 的主要功能（预防多不饱和膜脂质氧化）中的作用。
