Hitchcock P B, Mason R, Thomas K M, Shipley G G
Proc Natl Acad Sci U S A. 1974 Aug;71(8):3036-40. doi: 10.1073/pnas.71.8.3036.
Crystals of 1,2 dilauroyl-DL-phosphatidyl-ethanolamine:acetic acid are monoclinic with a = 46.2, b = 7.77, c = 9.95 A, beta = 92.0 degrees ; space group P2(1)/c. The structural analysis, based on the visual estimates of 1467 reflection intensities, was achieved by direct methods, and least squares analysis convergence was to R(1) = 0.28. There are marked differences between the observed molecular conformation and those that have been predicted theoretically. The mean planes containing the lipid chains are essentially parallel to one another; the phosphodiester moiety has a double gauche conformation, while intermolecular hydrogen bonding modifies the conformation that could be anticipated for an isolated phosphatidylethanolamine molecule. The intermolecular packing produces the classical lipid bilayer structure, adjacent lipid bilayers being separated by acetic acid molecules of crystallization. The hydrocarbon chain packing can be considered either as a quasi-hexagonal type or as a complex orthorhombic subcell arrangement. One-dimensional electron density profiles across the lipid bilayer at increasing resolution clearly demonstrate the origin of features present on the low resolution profiles of both model and natural membranes.
1,2-二月桂酰-DL-磷脂酰乙醇胺：乙酸晶体为单斜晶系，a = 46.2，b = 7.77，c = 9.95 Å，β = 92.0°；空间群P2(1)/c。基于对1467个反射强度的目测估计进行结构分析，采用直接法完成，最小二乘法分析收敛到R(1) = 0.28。观察到的分子构象与理论预测的构象之间存在显著差异。包含脂链的平均平面基本相互平行；磷酸二酯部分具有双gauche构象，而分子间氢键改变了孤立磷脂酰乙醇胺分子可能预期的构象。分子间堆积产生经典的脂质双层结构，相邻脂质双层被结晶的乙酸分子隔开。烃链堆积可被视为准六边形类型或复杂的正交亚晶胞排列。以不断提高的分辨率对脂质双层进行的一维电子密度分布清楚地证明了模型膜和天然膜低分辨率分布中特征的来源。
