To date X-ray protein crystallography is the most successful technique available for the determination of high-resolution 3D structures of biological molecules and their complexes. In X-ray protein crystallography the structure of a protein is refined against the set of observed Bragg reflections from a protein crystal. The resolution of the refined protein structure is limited by the highest angle at which Bragg reflections can be observed. In addition, the Bragg reflections alone are typically insufficient (by a factor of two) to determine the structureab initio, and so prior information is required. Crystals formed from an imperfect packing of the protein molecules may also exhibit continuous diffraction between and beyond these Bragg reflections. When this is due to random displacements of the molecules from each crystal lattice site, the continuous diffraction provides the necessary information to determine the protein structure without prior knowledge, to a resolution that is not limited by the angular extent of the observed Bragg reflections but instead by that of the diffraction as a whole. This article presents an iterative projection algorithm that simultaneously uses the continuous diffraction as well as the Bragg reflections for the determination of protein structures. The viability of this method is demonstrated on simulated crystal diffraction.

中文翻译：

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平移无序晶体衍射的 Ab 初始定相

迄今为止，X 射线蛋白质晶体学是用于确定生物分子及其复合物的高分辨率 3D 结构的最成功的技术。在 X 射线蛋白质晶体学中，根据从蛋白质晶体观察到的一组布拉格反射来细化蛋白质的结构。精制蛋白质结构的分辨率受到观察布拉格反射的最高角度的限制。此外，仅布拉格反射通常不足以（两倍）来确定结构从头开始，因此需要先验信息。由不完美的蛋白质分子堆积形成的晶体也可能在这些布拉格反射之间和之外表现出连续的衍射。当这是由于分子从每个晶格位点的随机位移引起时，连续衍射提供了必要的信息，可以在没有先验知识的情况下确定蛋白质结构，其分辨率不受观察到的布拉格反射的角度范围限制，而是由通过整体衍射的结果。本文提出了一种迭代投影算法，该算法同时使用连续衍射和布拉格反射来确定蛋白质结构。该方法的可行性在模拟晶体衍射中得到了证明。