Algorithm for Reconstruction of 3D Images of Nanorice Particles from Diffraction Patterns of Two Particles in Independent Random Orientations with an X-ray Laser
Algorithm for Reconstruction of 3D Images of Nanorice Particles from Diffraction Patterns of Two Particles in Independent Random Orientations with an X-ray Laser
复制标题
使用 X 射线激光根据独立随机方向的两个粒子的衍射图案重建纳米粒子 3D 图像的算法
DOI：
10.3390/app7070646
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
D. Saldin
中科院分区：
文献类型：
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作者：
Sung Soon Kim;S. Wibowo;D. Saldin
角相关法从随机定向粒子的衍射图中恢复量，正如期望用x射线自由电子激光器（XFEL）测量的那样，与单个粒子衍射体积的球谐膨胀系数的二次函数成正比。我们以前已经证明，有可能重建随机定向的二十面体或螺旋状病毒，从这些相关性的所有测量衍射图案的平均值。我们在论文中指出，即使是直径为50 a左右的更简单的粒子结构，由更重的原子元素组成（以增强散射），也可以用这种技术来解决XFEL衍射图重建的测试案例。尽管在类似的物体（长形球体）上已有较早的工作，但目前技术的一个优点是，它不仅可以像基于角散射的非重叠δ函数所建议的那样，用于单粒子的衍射模式。据此，我们从衍射图中计算了一般粒子图像的对相关和三重相关的角动量展开，并按标准方法重建了这些图像。尽管图像看起来几乎相同，但由于来自不同粒子的散射波之间可能存在建设性或破坏性干涉，我们并不完全清楚角相关性是否与不同数量的粒子完全相同。当然，我们知道，对于组成衍射图样的大量粒子，相关关系收敛于单个粒子的相关关系。用一个和两个粒子重建的图像之间缺乏完美的一致性可能是由于在溶液散射的情况下没有发现的不抵消的建设性和破坏性条件。
The method of angular correlations recovers quantities from diffraction patterns of randomly oriented particles, as expected to be measured with an X-ray free electron laser (XFEL), proportional to quadratic functions of the spherical harmonic expansion coefficients of the diffraction volume of a single particle. We have previously shown that it is possible to reconstruct a randomly oriented icosahedral or helical virus from the average over all measured diffraction patterns of such correlations. We point out in this paper that a structure of even simpler particles of 50 A or so in diameter and consisting of heavier atomic elements (to enhance scattering) that has been used as a test case for reconstructions from XFEL diffraction patterns can also be solved by this technique. Even though there has been earlier work on similar objects (prolate spheroids), one advantage of the present technique is its potential to also work with diffraction patterns not only due to single particles as has been suggested on the basis on nonoverlapping delta functions of angular scattering. Accordingly, we calculated from the diffraction patterns the angular momentum expansions of the pair correlations and triple correlations for general particle images and reconstructed those images in the standard way. Although the images looked pretty much the same, it is not totally clear to us that the angular correlations are exactly the same as different numbers of particles due to the possibility of constructive or destructive interference between the scattered waves from different particles. It is of course known that, for a large number of particles contributing to a diffraction parttern, the correlations converge to that of a single particle. It could be that the lack of perfect agreement between the images reconstructed with one and two particles is due to uncancelling constructive and destructive conditions that are not found in the case of solution scattering.