Analysis of electron microscope images and electron diffraction patterns of thin crystals of phi 29 connectors in ice.
Analysis of electron microscope images and electron diffraction patterns of thin crystals of phi 29 connectors in ice.
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冰中 phi 29 连接器薄晶体的电子显微镜图像和电子衍射图案分析。
DOI：
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发表时间：
1994
影响因子：
5.6
通讯作者：
R. Henderson
中科院分区：
文献类型：
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作者：
J. Valpuesta;J. Carrascosa;R. Henderson
使用低剂量显微镜和衍射记录了phi 29连接器的冷冻水合薄晶体的图像和衍射图案。在两种情况下获得的分辨率分别为7和4 A，从而表明该标本适合于高分辨率研究。七个最好的图像和三个最好的电子衍射图案进行了半定量分析。最佳图像显示每个晶胞（165 A x 165 A）存在两个连接器，每个连接器具有内部4重轴，并且在空间群p42（1）2中通过2重和2重螺旋轴彼此相关。最佳图像内的内部相位比较显示p42（1）2及其所有亚组具有良好的相位残差。考虑到可能的晶体倾斜和样品漂移，其他图像与该解释一致。我们得出结论，最可能的晶体空间群是p42（1）2。电子衍射图案与这一分配是一致的，但没有一个图案显示出预期的精确的422对称性，几乎可以肯定是因为晶体轻微倾斜（2至5度）。
Images and diffraction patterns of frozen-hydrated thin crystals of phi 29 connectors were recorded using low dose microscopy and diffraction. The resolution obtained in two cases was 7 and 4 A, thus showing the suitability of this specimen for high-resolution studies. Seven of the best images and three of the best electron diffraction patterns were analysed semiquantitatively. The best image showed the presence of two connectors per unit cell (165 A x 165 A), each having an internal 4-fold axis and being related to one-another by 2-fold and 2-fold screw axes in the space group p42(1)2. Internal phase comparison within the best image showed good phase residuals for p42(1)2 and all its sub-groups. The other images were consistent with this interpretation taking into consideration the possible crystal tilt and specimen drift. We conclude that the most likely crystal space group is p42(1)2. Electron diffraction patterns were consistent with this assignment, but none of the patterns showed the precise 422 symmetry expected, almost certainly because the crystals were slightly tilted (2 to 5 degrees).