Signal to noise considerations for single crystal femtosecond time resolved crystallography of the Photoactive Yellow Protein.
Signal to noise considerations for single crystal femtosecond time resolved crystallography of the Photoactive Yellow Protein.
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光活性黄色蛋白的单晶飞秒时间分辨晶体学的信噪比考虑因素。
DOI：
10.1039/c4fd00011k
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发表时间：
2014
影响因子：
3.4
通讯作者：
Van Thor JJ
中科院分区：
文献类型：
--
作者：
Van Thor JJ
飞秒时间分辨的泵浦-探测蛋白质X射线晶体学需要高度精确的测量光致结构因子振幅差。在飞秒光解的光活性黄蛋白的单个P63晶体的情况下，它表明，光化学动力学放置一个相当大的限制，由于需要拉伸和添加二阶色散，以产生阈值浓度水平的相互作用区域中可实现的时间分辨率。在这里，我们报告使用一个“准CW”的方法，使用旋转方法与单色辐射和2 eV带宽在9.465千电子伏的直线加速器相干光源在SASE模式下操作。一个重要的布拉格反射强度噪声的来源被确定从模式结构和抖动的组合与非常小的马赛克扩展的晶体和非常低的XFEL源的收敛。从实验收集的X射线脉冲强度与测得的摇摆曲线的准确性与三维反射近似的“准CW”旋转方法与脉冲源建模。该模型扩展到预测合并统计最近证明自我播种模式产生的脉冲串具有改善的稳定性，除了外推到单晶实验增加马赛克蔓延。结果表明，噪声水平可以以这种方式充分建模，表明大的强度波动主导合并的信噪比（I/σI）值。此外，这些结果预测，使用自播种模式与更多的镶嵌晶体，可以获得足够的精度，以解决典型的光致结构因子振幅差异，从代表性的同步加速器结果。
Femtosecond time resolved pump–probe protein X-ray crystallography requires highly accurate measurements of the photoinduced structure factor amplitude differences. In the case of femtosecond photolysis of single P63 crystals of the Photoactive Yellow Protein, it is shown that photochemical dynamics place a considerable restraint on the achievable time resolution due to the requirement to stretch and add second order dispersion in order to generate threshold concentration levels in the interaction region. Here, we report on using a ‘quasi-cw’ approach to use the rotation method with monochromatic radiation and 2 eV bandwidth at 9.465 keV at the Linac Coherent Light Source operated in SASE mode. A source of significant Bragg reflection intensity noise is identified from the combination of mode structure and jitter with very small mosaic spread of the crystals and very low convergence of the XFEL source. The accuracy with which the three dimensional reflection is approximated by the ‘quasi-cw’ rotation method with the pulsed source is modelled from the experimentally collected X-ray pulse intensities together with the measured rocking curves. This model is extended to predict merging statistics for recently demonstrated self seeded mode generated pulse train with improved stability, in addition to extrapolating to single crystal experiments with increased mosaic spread. The results show that the noise level can be adequately modelled in this manner, indicating that the large intensity fluctuations dominate the merged signal-to-noise (I/σI) value. Furthermore, these results predict that using the self seeded mode together with more mosaic crystals, sufficient accuracy may be obtained in order to resolve typical photoinduced structure factor amplitude differences, as taken from representative synchrotron results.
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蓝光光感受器 PYP 和 AppA 从初级光化学到生物功能
影响因子：
3.1
作者：
M. Horst;W. Laan;S. Yeremenko;A. Wende;P. Palm;D. Oesterhelt;K. Hellingwerf
通讯作者：
K. Hellingwerf
DOI：
10.1073/pnas.0409035102
发表时间：
2005-05-17
影响因子：
11.1
作者：
Ihee, H;Rajagopal, S;Moffat, K
通讯作者：
Moffat, K
影响因子：
56.9
作者：
Perman, B;Srajer, V;Moffat, K
通讯作者：
Moffat, K
影响因子：
6.8
作者：
Neutze R;Moffat K
通讯作者：
Moffat K
DOI：
--
发表时间：
--
期刊：
--
影响因子：
--
作者：
A. G. W. Leslie
通讯作者：
A. G. W. Leslie