Li Xuanxuan, Spence John C H, Hogue Brenda G, Liu Haiguang
Complex Systems Division, Beijing Computational Science Research Center, 8 East Xibeiwang Road, Haidian, Beijing 100193, People's Republic of China.
Department of Engineering Physics, Tsinghua University, 30 ShuangQing Rd, Haidian, Beijing 100084, People's Republic of China.
IUCrJ. 2017 Sep 22;4(Pt 6):741-750. doi: 10.1107/S2052252517012398. eCollection 2017 Nov 1.
X-ray free-electron lasers (XFELs) provide new opportunities for structure determination of biomolecules, viruses and nanomaterials. With unprecedented peak brilliance and ultra-short pulse duration, XFELs can tolerate higher X-ray doses by exploiting the femtosecond-scale exposure time, and can thus go beyond the resolution limits achieved with conventional X-ray diffraction imaging techniques. Using XFELs, it is possible to collect scattering information from single particles at high resolution, however particle heterogeneity and unknown orientations complicate data merging in three-dimensional space. Using the Linac Coherent Light Source (LCLS), synthetic inorganic nanocrystals with a core-shell architecture were used as a model system for proof-of-principle coherent diffractive single-particle imaging experiments. To deal with the heterogeneity of the core-shell particles, new computational methods have been developed to extract the particle size and orientation from the scattering data to assist data merging. The size distribution agrees with that obtained by electron microscopy and the merged data support a model with a core-shell architecture.
X射线自由电子激光（XFEL）为生物分子、病毒和纳米材料的结构测定提供了新机会。凭借前所未有的峰值亮度和超短脉冲持续时间，XFEL通过利用飞秒级的曝光时间能够承受更高的X射线剂量，因此可以突破传统X射线衍射成像技术所达到的分辨率极限。使用XFEL，可以从单个粒子以高分辨率收集散射信息，然而粒子的异质性和未知取向使三维空间中的数据合并变得复杂。利用直线加速器相干光源（LCLS），具有核壳结构的合成无机纳米晶体被用作原理验证相干衍射单粒子成像实验的模型系统。为了处理核壳粒子的异质性，已开发出新的计算方法，从散射数据中提取粒子尺寸和取向以辅助数据合并。尺寸分布与通过电子显微镜获得的结果一致，并且合并后的数据支持具有核壳结构的模型。
