Triiodide derivatization and combinatorial counter-ion replacement:: two methods for enhancing phasing signal using laboratory Cu Kα X-ray equipment
Triiodide derivatization and combinatorial counter-ion replacement:: two methods for enhancing phasing signal using laboratory Cu Kα X-ray equipment
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DOI：
10.1107/s0907444902005486
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发表时间：
2002-06-01
影响因子：
2.2
通讯作者：
Bricogne, G
中科院分区：
文献类型：
--
作者：
Evans, G;Bricogne, G
本文介绍了在室内X射线设备上进行的一系列在铜卡尔法波长下进行的实验，这些实验研究了通过(I)用KI/I-2浸泡三碘/碘化物和(Ii)用短低温方法引入反离子组合来增强实验相位信号的两种可能性。对五种蛋白质的三碘代衍生物晶体结构进行了精炼，结果表明，在分子表面、分子内和分子间空穴中，碘可以通过疏水作用和氢键作用以多碘离子和单碘离子的形式结合。在三种情况下，可以使用内部SAD和SIRAS数据通过AutoSHARP自动确定结构。以Na~+和Cs~+为阳离子，I~-和Cl~-为阴离子的多种盐的组合反离子置换研究表明，对于蛋清溶菌酶，与使用天然和单一短浸泡导数数据集的SIRAS方法相比，组合使用盐的相变信号得到了显著的改善。
A series of experiments performed at Cu Kalpha wavelength on in-house X-ray equipment are presented which investigate two possibilities for enhancing the experimental phasing signal by means of (i) triiodide/iodide soaks using KI/I-2 and (ii) combinations of counter-ions introduced using the short cryosoak method. Triiodide-derivative crystal structures for five test proteins have been refined and reveal that iodine can bind as polyiodide and single iodide ions through hydrophobic and hydrogen-bonding interactions both at the molecular surface and in intramolecular and intermolecular cavities. In three cases, the structures could be automatically determined with autoSHARP using in-house SAD and SIRAS data. The investigation of combinatorial counter-ion replacement using multiple salts with Na+ and Cs+ as cations and I- and Cl- as anions reveals that, for the case of hen egg-white lysozyme, significant improvement in phasing signal is obtained by the combined use of salts compared with SIRAS methods using native and single short-soak derivative data sets.