X-ray free-electron lasers (XFELs) have allowed the imaging of nanoscale samples in near-physiological conditions. To achieve three-dimensional (3D) nanostructural reconstruction, many challenges need to be addressed, such as sample delivery for data collection and data processing of noisy diffraction patterns. Here, we provided a demonstration of the 3D structure reconstruction of a gold nanoparticle from XFEL diffraction data measured at the SPring-8 Angstrom Compact Free-Electron Laser using microliquid enclosure arrays (MLEAs) sample holders. MLEAs enable in-solution measurements, however, they induce a significant amount of background noise. Thus, we performed a series of data analyses to identify the diffraction patterns suitable for 3D reconstruction as well as nonhit patterns to estimate the background noise. The background subtraction from the data significantly improved the quality of the restored structure, with the resolution estimated to be 5 nm using Fourier shell correlation. Our paper has revealed the notable potential of XFEL imaging using MLEAs in combination with the developed data-analysis protocol.

中文翻译：

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使用 X 射线自由电子激光单粒子分析法测定溶液中金纳米三角形的三维结构

X 射线自由电子激光器 (XFEL) 允许在接近生理条件下对纳米级样品进行成像。为了实现三维 (3D) 纳米结构重建，需要解决许多挑战，例如用于数据收集的样本交付和噪声衍射图案的数据处理。在这里，我们展示了使用微液体外壳阵列 (MLEA) 样品架在 SPring-8 埃紧凑型自由电子激光器上测量的 XFEL 衍射数据对金纳米粒子的 3D 结构重建的演示。MLEA 可以进行溶液内测量，但是，它们会产生大量的背景噪声。因此，我们进行了一系列数据分析，以确定适合 3D 重建的衍射图案以及用于估计背景噪声的非命中图案。从数据中减去背景显着提高了恢复结构的质量，使用傅里叶壳相关性估计分辨率为 5 nm。我们的论文揭示了使用 MLEA 与开发的数据分析协议相结合的 XFEL 成像的显着潜力。