Molecular dynamics investigation of the structure of a fully hydrated gel-phase dipalmitoylphosphatidylcholine bilayer.
Molecular dynamics investigation of the structure of a fully hydrated gel-phase dipalmitoylphosphatidylcholine bilayer.
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DOI：
10.1016/s0006-3495(96)79623-6
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发表时间：
1996-02
影响因子：
3.4
通讯作者：
K. Tu;Douglas J. Tobias;J. Blasie;Michael L. Klein
中科院分区：
文献类型：
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作者：
K. Tu;Douglas J. Tobias;J. Blasie;Michael L. Klein
报道了Nw=11.8水分子/脂的凝胶相二棕榈酰磷脂酰胆碱双层膜在19℃下的恒压恒温分子动力学模拟结果，并与各种X射线和中子衍射数据进行了详细的比较。特定碳原子沿双层法线的平均位置、层间距和电子密度分布与中子和X射线衍射结果非常吻合。每脂比表面积和面内碳氢链结构细节与广角X射线衍射结果吻合较好。唯一显著的偏差是链在双层中心以折叠的方式相遇，尽管它们应该是平行的。在本工作中的新发现包括观察到双峰头群的定向分布。此外，我们发现在碳氢链末端附近有相当数量的Guche构象，并且，除了验证了先前关于碳氢链中存在部分旋转有序的建议外，还发现给定分子中的两个链在旋转方面是不等价的。最后，我们研究了脂质/水的界面，发现水渗透到头基下面，但不像羰基那么远，磷酸盐强烈的水化几乎只在非酯化的氧原子上进行，而氨基的水化更分散，一些水分子集中在甲基之间的凹槽中。
We report the results of a constant pressure and temperature molecular dynamics simulation of a gel-phase dipalmitoylphosphatidylcholine bilayer with nw=11.8 water molecules/lipid at 19 degrees C. The results of the simulation were compared in detail with a variety of x-ray and neutron diffraction data. The average positions of specific carbon atoms along the bilayer normal and the interlamellar spacing and electron density profile were in very good agreement with neutron and x-ray diffraction results. The area per lipid and the details of the in-plane hydrocarbon chain structure were in excellent agreement with wide-angle x-ray diffraction results. The only significant deviation is that the chains met in a pleated arrangement at the bilayer center, although they should be parallel. Novel discoveries made in the present work include the observation of a bimodal headgroup orientational distribution. Furthermore, we found that there are a significant number of gauche conformations near the ends of the hydrocarbon chains and, in addition to verifying a previous suggestion that there is partial rotational ordering in the hydrocarbon chains, that the two chains in a given molecule are inequivalent with respect to rotations. Finally, we have investigated the lipid/water interface and found that the water penetrates beneath the headgroups, but not as far as the carbonyl groups, that the phosphates are strongly hydrated almost exclusively at the nonesterified oxygen atoms, and that the hydration of the ammonium groups is more diffuse, with some water molecules concentrated in the grooves between the methyl groups.