用分子动力学方法模拟了280,310和350 K-卜a-生育酚在二豆蔻酞磷脂酞胆碱、二豆蔻酞磷脂酞乙醇胺、二硬脂酞磷脂酞胆碱和二硬脂酞磷脂酞乙醇胺双层膜中的性质,包括了空间位置、氢键、取向和动力学性质,取得了如下的结论.第一,生育酚头部的羟基一般位于脂双层亲疏水界面的下方,升高温度将促进羟基向膜双层的中心移动,在350K时观察到了在上下两个单层间的翻转.第二,生育酚主要与磷脂的酯基形成氢键,几乎不与磷脂酞乙醇胺的氨基形成氢键;比较生育酚与磷脂酞胆碱和乙醇胺形成的氢键后发现,后者更稳定.第三,生育酚的头部在膜中取向多变,与膜的法线夹角不固定,尾部的构象也很复杂.第四,在温度较低时,生育酚的侧向扩散系数与磷脂的相当,但在350K时其扩散速度明显加快;在垂直方向生育酚的扩散速度很慢.%Molecular dynamics simulations of α-tocopherol in a number of saturated phospholipid bilayers were performed at 280, 310, and 350 K. The phospholipids contained either short acyl tails, i.e.,dimyristoylphosphatidylcholine and dimyristoylphosphatidylethanolamine or long acyl tails, namely distearoylphosphatidylcholineanddistearoylphosphatidylethanolamine.Thepreferentialposition,hydrogen bonding, orientation, and dynamic properties of α-tocopherol in the bilayers were examined in detail and several conclusions were made. First, the hydroxyl group of a-tocopherol generally remains beneath the interfacial region of the lipid bilayers and it shifts toward the bilayer mid-plane with an increase in temperature. At 350 K it flip-flops between the upper and lower leaflets in the four lipid bilayers. Second,α-tocopherol mainly forms hydrogen bonds with the carbonyl ester oxygen in the lipid head groups and hardly forms hydrogen bonds with the amino groups in the phosphatidylethanolamine (PE) bilayers.Hydrogen bonding with PEs is more stable than hydrogen bonding with phosphatidylcholines (PCs) at low temperatures. Third, a-tocopherol's head group has fluctuating tilt angles relative to the normal of the lipid bilayers and the tail has many different conformations. Fourth, the lateral diffusion rate of a-tocopherol is comparable to that of phospholipid molecules at low temperature and it diffuses much faster than lipids at 350 K. The diffusion rate in the direction perpendicular to the membrane surface is much slower than the lateral diffusion rate.
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