Tocopherol Activity Correlates with Its Location in a Membrane: A New Perspective on the Antioxidant Vitamin E

We show evidence of an antioxidant mechanism for vitamin E which correlates strongly with its physical location in a model lipid bilayer. These data address the overlooked problem of the physical distance between the vitamin's reducing hydrogen and lipid acyl chain radicals. Our combined data from neutron diffraction, NMR, and UV spectroscopy experiments all suggest that reduction of reactive oxygen species and lipid radicals occurs specifically at the membrane's hydrophobic-hydrophilic interface. The latter is possible when the acyl chain "snorkels" to the interface from the hydrocarbon matrix. Moreover, not all model lipids are equal in this regard, as indicated by the small differences in vitamin's location. The present result is a clear example of the importance of lipid diversity in controlling the dynamic structural properties of biological membranes. Importantly, our results suggest that measurements of aToc oxidation kinetics, and its products, should be revisited by taking into consideration the physical properties of the membrane in which the vitamin resides.

我们展示了维生素E的一种抗氧化机制的证据，该机制与其在模型脂质双层中的物理位置密切相关。这些数据解决了被忽视的维生素的还原氢与脂质酰基链自由基之间物理距离的问题。我们从中子衍射、核磁共振和紫外光谱实验中综合得到的数据都表明，活性氧物质和脂质自由基的还原特别发生在膜的疏水 - 亲水界面。当酰基链从烃基质“浮”到界面时，后者是可能的。此外，并非所有的模型脂质在这方面都是相同的，正如维生素位置的微小差异所表明的那样。目前的结果是脂质多样性在控制生物膜动态结构特性方面重要性的一个明显例子。重要的是，我们的结果表明，应该考虑维生素所处膜的物理性质，重新审视α - 生育酚氧化动力学及其产物的测量。