Oka Toshihiko, Miura Keiko, Inoue Katsuaki, Ueki Tatzuo, Yagi Naoto
Department of Physics, Faculty of Science and Technology, Keio University, Japan.
J Synchrotron Radiat. 2006 May;13(Pt 3):281-4. doi: 10.1107/S0909049506004766. Epub 2006 Apr 13.
X-ray diffraction patterns from a film of oriented purple membranes, which comprise two-dimensional crystals of bacteriorhodopsin (BR) trimers, were recorded with a 1 m-pathlength Guinier-type camera at SPring-8 BL40B2. A well focused X-ray beam and a camera with a high angular resolution of 0.024 degrees enabled a powder diffraction profile with very sharp and well separated peaks to be obtained up to a resolution of 2.3 A. Using integrated diffraction intensities up to a Bragg spacing of 4.2 A, a cluster of bulky amino acid residues and the head group of the BR chromophore are apparent in the electron density map projected along the membrane normal. Thus, a combination of synchrotron X-rays and large Guinier camera can be used for analyzing the conformational changes of BR in the intact state. In addition, the method might be extended to the structural analysis of film materials composed of two-dimensional arrays of nanoparticles.
在SPring-8的BL40B2光束线，使用1米光程的吉尼尔型相机记录了来自取向紫膜薄膜的X射线衍射图谱，该紫膜由细菌视紫红质（BR）三聚体的二维晶体组成。聚焦良好的X射线束和角分辨率高达0.024度的相机，使得在高达2.3 Å的分辨率下能够获得具有非常尖锐且分离良好的峰的粉末衍射图谱。利用高达4.2 Å布拉格间距的积分衍射强度，在沿膜法线投影的电子密度图中，可以明显看到一组庞大的氨基酸残基和BR发色团的头部基团。因此，同步加速器X射线和大型吉尼尔相机的组合可用于分析完整状态下BR的构象变化。此外，该方法可能会扩展到由纳米颗粒二维阵列组成的薄膜材料的结构分析。
