Phasing of novel macromolecular crystal structures has been challenging since the start of structural biology. Making use of anomalous diffraction of natively present elements, such as sulfur and phosphorus, for phasing has been possible for some systems, but hindered by the necessity to access longer X-ray wavelengths in order to make most use of the anomalous scattering contributions of these elements. Presented here are the results from a first successful experimental phasing study of a macromolecular crystal structure at a wavelength close to the sulfur K edge. This has been made possible by the in-vacuum setup and the long-wavelength optimised experimental setup at the I23 beamline at Diamond Light Source. In these early commissioning experiments only standard data collection and processing procedures have been applied, in particular no dedicated absorption correction has been used. Nevertheless the success of the experiment demonstrates that the capability to extract phase information can be even further improved once data collection protocols and data processing have been optimised.

中文翻译：

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长波大分子晶体学-第一个成功的天然SAD实验，靠近硫的边缘。

自从结构生物学开始以来，新型大分子晶体结构的定相就一直具有挑战性。在某些系统中，可以利用自然存在的元素（如硫和磷）的异常衍射进行定相，但由于必须利用更长的X射线波长而受到阻碍，以便最大程度地利用这些元素的异常散射贡献元素。这里展示的是在接近硫K边缘的波长下对大分子晶体结构进行的首次成功的实验定相研究的结果。钻石光源的I23光束线上的真空设置和优化的长波长实验设置使之成为可能。在这些早期的调试实验中，仅采用了标准的数据收集和处理程序，特别是没有使用专门的吸收校正。然而，实验的成功表明，一旦数据收集协议和数据处理得到优化，提取相位信息的能力将得到进一步提高。