Sun W J, Tristram-Nagle S, Suter R M, Nagle J F
Department of Physics, Carnegie Mellon University, Pittsburg, PA 15213, USA.
Proc Natl Acad Sci U S A. 1996 Jul 9;93(14):7008-12. doi: 10.1073/pnas.93.14.7008.
The phases of the x-ray form factors are derived for the ripple (Pbeta') thermodynamic phase in the lecithin bilayer system. By combining these phases with experimental intensity data, the electron density map of the ripple phase of dimyristoyl-phosphatidylcholine is constructed. The phases are derived by fitting the intensity data to two-dimensional electron density models, which are created by convolving an asymmetric triangular ripple profile with a transbilayer electron density profile. The robustness of the model method is indicated by the result that many different models of the transbilayer profile yield essentially the same phases, except for the weaker, purely ripple (0,k) peaks. Even with this residual ambiguity, the ripple profile is well determined, resulting in 19 angstroms for the ripple amplitude and 10 degrees and 26 degrees for the slopes of the major and the minor sides, respectively. Estimates for the bilayer head-head spacings show that the major side of the ripple is consistent with gel-like structure, and the minor side appears to be thinner with lower electron density.
推导了卵磷脂双层系统中波纹（Pbeta'）热力学相的X射线形状因子的相位。通过将这些相位与实验强度数据相结合，构建了二肉豆蔻酰磷脂酰胆碱波纹相的电子密度图。这些相位是通过将强度数据拟合到二维电子密度模型而推导出来的，该模型是通过将不对称三角形波纹轮廓与跨双层电子密度轮廓进行卷积而创建的。模型方法的稳健性体现在这样的结果中：除了较弱的纯波纹（0,k）峰外，许多不同的跨双层轮廓模型产生的相位基本相同。即使存在这种残留的模糊性，波纹轮廓也能很好地确定，得到波纹幅度为19埃，主侧边和次侧边的斜率分别为10度和26度。双层头对头间距的估计表明，波纹的主侧边与凝胶状结构一致，次侧边似乎更薄，电子密度更低。
