Mini-beam collimator enables microcrystallography experiments on standard beamlines
Mini-beam collimator enables microcrystallography experiments on standard beamlines
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DOI：
10.1107/s0909049508040612
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发表时间：
2009-03-01
影响因子：
2.5
通讯作者：
Smith, Janet L.
中科院分区：
文献类型：
--
作者：
Fischetti, Robert F.;Xu, Shenglan;Smith, Janet L.
来自第三代同步加速器设备的波荡器源的高亮度X射线束是解决重要且具有挑战性的生物大分子和复合物的晶体结构的极好工具。然而，许多最重要的结构靶产生的晶体对于来自波荡器源的“标准”束来说太小或太不均匀，类似于垂直方向上的25-50 μ m（FWHM）和水平方向上的50-100 μ m。虽然许多同步加速器设施具有用于其他应用的微聚焦光束线，但这种用于大分子晶体学的能力是ESRF的ID-13开创的。美国国家普通医学科学研究所和美国国家癌症研究所合作访问小组（GM/CA-CAT）在APS的双倾斜波荡器光束线提供高强度聚焦光束，在样品位置的最小焦点尺寸为20 μ m x 65 μ m。为了满足日益增长的用户对光束的需求，以研究10 μ m或更小的样品，开发了一种“迷你光束”装置，该装置可以将聚焦光束调节到5 μ m或10 μ m（FWHM）直径，并具有高强度。微光束在水平和垂直方向上都具有对称的高斯形状，并将聚焦光束的垂直发散角减小了25%。通过实施前向散射和后向散射防护，实现了背景的显著减少。自2008年2月以来，独特的三重准直仪设备一直在两条波荡器光束线上常规使用，允许用户只需点击鼠标即可快速交换两种尺寸的聚焦光束和调节迷你光束。设备和光束在许多小时的常规操作中保持稳定。快速交换能力极大地促进了样品筛选，并产生了几种用较大聚焦光束无法获得的结构。
The high-brilliance X-ray beams from undulator sources at third-generation synchrotron facilities are excellent tools for solving crystal structures of important and challenging biological macromolecules and complexes. However, many of the most important structural targets yield crystals that are too small or too inhomogeneous for a 'standard' beam from an undulator source, similar to 25-50 mu m (FWHM) in the vertical and 50-100 mu m in the horizontal direction. Although many synchrotron facilities have microfocus beamlines for other applications, this capability for macromolecular crystallography was pioneered at ID-13 of the ESRF. The National Institute of General Medical Sciences and National Cancer Institute Collaborative Access Team (GM/CA-CAT) dual canted undulator beamlines at the APS deliver high-intensity focused beams with a minimum focal size of 20 mu m x 65 mu m at the sample position. To meet growing user demand for beams to study samples of 10 mu m or less, a 'mini-beam' apparatus was developed that conditions the focused beam to either 5 mu m or 10 mu m (FWHM) diameter with high intensity. The mini-beam has a symmetric Gaussian shape in both the horizontal and vertical directions, and reduces the vertical divergence of the focused beam by 25%. Significant reduction in background was achieved by implementation of both forward- and back-scatter guards. A unique triple-collimator apparatus, which has been in routine use on both undulator beamlines since February 2008, allows users to rapidly interchange the focused beam and conditioned mini-beams of two sizes with a single mouse click. The device and the beam are stable over many hours of routine operation. The rapid-exchange capability has greatly facilitated sample screening and resulted in several structures that could not have been obtained with the larger focused beam.