Anomalous dispersion with edges in the soft X-ray region: First results of diffraction from single crystals of trypsin near the K-absorption edge of sulfur
Anomalous dispersion with edges in the soft X-ray region: First results of diffraction from single crystals of trypsin near the K-absorption edge of sulfur
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DOI：
10.1107/s0909049597009059
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发表时间：
1997-09-01
影响因子：
2.5
通讯作者：
Stuhrmann, HB
中科院分区：
文献类型：
--
作者：
Stuhrmann, S;Bartels, KS;Stuhrmann, HB
在硫的X-射线K-吸收边附近的波长在5埃左右的波长处的X-射线衍射的异常色散已被应用于从硫酸铵溶液中获得的胰蛋白酶的单晶。基于在胰蛋白酶中硫的K吸收边缘附近的三个波长处测量的775个独特反射（+183个Bijvoet mates）的多波长色散方法（两个甲硫氨酸和六个胱氨酸的二硫键）以4埃的分辨率再现了胰蛋白酶结构的已知特征。胱氨酸二硫键的各向异性反常散射。多波长反常溶剂对比度显示在硫酸根离子的K-吸收边附近的波长处，其相对于胰蛋白酶中的硫被移动10 eV至更高的能量。分析了胰蛋白酶在2.5 M硫酸铵溶液中的复杂对比度对低阶反射色散的影响。本文介绍了测量5埃以上长波长X射线衍射反常色散所需的专用衍射仪的特点。一个突出的是由四个多线正比计数器组成的探测器系统。并与成像板的效率进行了比较。本文介绍了胰蛋白酶单晶软X射线衍射辐射损伤的影响，并讨论了可能的补救措施。
Anomalous dispersion of X-ray diffraction at wavelengths near the X-ray K-absorption edge of sulfur at wavelengths around 5 Angstrom has been applied to single crystals of trypsin obtained from an ammonium sulfate solution. The multiwavelength anomalous-dispersion method based on 775 unique reflections (+183 Bijvoet mates) measured at three wavelengths near the K-absorption edge of sulfur in trypsin (two methionines and disulfide bridges of six cystines) reproduces the known features of the trypsin structure at a resolution of 4 Angstrom. It appears that there is anisotropic anomalous scattering from the disulfide bridges of cystine. The multiwavelength anomalous solvent contrast shows up at wavelengths near the K-absorption edge of the sulfate ions, which is shifted by 10 eV to higher energies with respect to that of sulfur in trypsin. The influence of the complex contrast of trypsin in 2.5 M ammonium sulfate on the dispersion of a low-order reflection is analyzed. The measurement of anomalous dispersion of X-ray diffraction at long wavelengths beyond 5 Angstrom requires a special diffractometer, the features of which are presented. An outstanding one is a detector system consisting of four multiwire proportional counters. Its efficiency is compared with that of imaging plates. The influence of radiation damage with soft X-ray diffraction from single crystals of trypsin is presented and possible remedies are discussed.