DISCUSSION PAPER: MOLECULAR STRUCTURES AND CONFORMATIONS OF THE PHOSPHOLIPIDS AND SPHINGOMYELINS *
DISCUSSION PAPER: MOLECULAR STRUCTURES AND CONFORMATIONS OF THE PHOSPHOLIPIDS AND SPHINGOMYELINS *
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讨论论文：磷脂和鞘磷脂的分子结构和构象 *
DOI：
10.1111/j.1749-6632.1972.tb54814.x
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发表时间：
1972
影响因子：
5.2
通讯作者：
M. Sundaralihgam
中科院分区：
文献类型：
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作者：
M. Sundaralihgam
在今天下午发表的之前的论文中，提出了各种膜模型，这些模型与从膜横截面的 X 射线衍射数据获得的电子密度分布相一致。 X射线方法受到严重限制，因为缺乏大量高分辨率数据，无法在分子水平上确定膜的结构，更不用说在原子分辨率上确定膜的结构了。由于膜衍射数据的缺乏，甚至无法确定其分子组成。然而，衍射方法的优点是能够提供电子密度分布，只要已知反射 X 射线振幅的相位角和有关膜化学成分的足够信息，电子密度分布可用于测试可用的膜结构模型或提出新的模型。 ROS 盘膜的结构就是一个典型的例子。 Blaurock 和 Wilkins * 早些时候通过对该膜的 X 射线研究表明，X 射线电子密度分布与磷脂双层一致。电子密度分布的主要特征是存在两个相距约 40 A 的峰。这些峰归因于脂质的磷酸基团以及烃链的中间低电子密度区域。 1970 年，Vanderkooi 和 Sundaralingam 提出了一种新的 ROS 膜模型，其中视紫红质分子“半浸没”在熟悉的 Danielli-Davson 脂质双层结构中。该模型与 ROS 膜上所有可用的物理化学数据一致。 Wilkins3 今天提到，他们最近使用改进的 X 射线数据对 ROS 膜进行的 X 射线研究揭示了电子密度分布中峰两侧的肩峰。他认为，这一特征可以通过假设视紫红质分子约为
In the previous papers that have been presented this afternoon, various membrane models were proposed that were consistent with the electron density profiles obtained from x-ray diffraction data of the cross-section of the membranes. The x-ray method is severely limited in that the lack of extensive high resolution data precludes the determination of the structure of a membrane at the molecular level, let alone at atomic resolution. The scarcity of diffraction data from membranes prevents even the determination of their molecular composition. The diffraction methods however, have the advantage of being able to provide electron density distributions which can be utilized in either testing available models of membrane structure or proposing new ones, provided that the phase angles of the reflected x-ray amplitudes and enough information on the chemical composition of the membrane are known. A case in point is the structure of the ROS disk membrane. Blaurock and Wilkins * showed earlier from their x-ray studies of this membrane that the x-ray electron density distribution was consistent with a bilayer of phospholipids. The main feature of the electron density profile was the presence of two peaks about 40 A apart. These peaks were attributed to the phosphate groups of the lipids, and the intervening low electron density region to the hydrocarbon chains. In 1970 Vanderkooi and Sundaralingam proposed a new model for the ROS membrane with the molecules of rhodopsin about “half-submerged” in the familiar Danielli-Davson lipid bilayer structure. This model was shown to be consistent with all available physicochemical data on the ROS membrane. Wilkins3 has mentioned today that their recent x-ray studies on the ROS membrane using improved x-ray data reveal shoulders on either side of the peak in the electron density profile. He suggests that this feature can be explained by assuming that rhodopsin molecules are about