发表机构
Max Planck Institute for the Structure and Dynamics of Matter; The Hamburg Centre for Ultrafast Imaging, Universität Hamburg; Laboratory of Molecular Biophysics, Department of Cell and Molecular Biology, Uppsala University; European XFEL; University of Stavanger; Biodesign Center for Applied Structural Discovery, Arizona State University; Department of Physics, Arizona State University; Department of Physics and Astronomy, Uppsala University; Deutsches Elektronen-Synchrotron DESY, Center for Free-Electron Laser Science CFEL; Dipartimento di Elettronica, Informazione e Bioingegneria (DEIB), Politecnico di Milano; INFN, Sezione di Milano; Department of Electrical and Computer Engineering, University of Canterbury; Department of Molecular Sciences and Nanosystems, Ca’ Foscari University of Venice; Department of Applied Physics, AlbaNova University Center, KTH Royal Institute of Technology; Leibniz Institute of Virology（马克斯·普朗克物质结构与动力学研究所; 汉堡超快成像中心，汉堡大学; 乌普萨拉大学生物细胞与分子生物学系分子生物物理实验室; 欧洲自由电子激光设施; 斯塔万格大学; 亚利桑那州立大学生物设计应用结构发现中心; 亚利桑那州立大学物理系; 乌普萨拉大学物理与天文系; 德国电子同步加速器研究所DESY，自由电子激光科学中心CFEL; 米兰理工大学电子、信息与生物工程系; 意大利国家核物理研究所米兰分部; 坎特伯雷大学电气与计算机工程系; 威尼斯卡福斯卡里大学分子科学与纳米系统系; 皇家理工学院阿尔巴诺瓦大学中心应用物理系; 莱布尼兹病毒学研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究利用X射线自由电子激光，通过电荷还原电喷雾电离制备样品、氦气交换降低背景散射，从32788个衍射图案重构出真空中孤立光系统I三聚体的三维电子密度，分辨率达3.8纳米，为单个大分子超快衍射成像奠定重要基础。
AI 中文摘要
利用强而超短的X射线脉冲对单个生物分子、病毒和细胞进行成像的前景，推动了X射线自由电子激光（XFEL）的发展。然而，小粒子的弱散射信号很容易被残留气体的背景所淹没，这迄今为止将相关应用限制在散射能力强的靶标上，如病毒、细胞器和细胞。在此，我们报告了利用单粒子衍射数据对一个分子量为1兆道尔顿（MDa）的孤立膜蛋白复合物——光系统I（PS I）进行的三维（3D）重构。PS I三聚体通过电荷还原电喷雾电离被气雾化，并注入欧洲XFEL光束中，部分氦气交换使背景散射降低了80%。从32788个随机取向的单个三聚体衍射图案中，我们重构出三维电子密度，分辨率达到3.8纳米，该分辨率受探测器几何结构的限制。该盘状密度约22纳米宽、10纳米厚，与去垢剂胶束中PS I三聚体的尺寸匹配，且与该复合物在真空中的分子动力学模拟预测的压缩状态以及天然质谱中观察到的结果一致。这些结果表明，膜蛋白复合物可以利用X射线激光在真空中进行成像，这是实现单个大分子超快衍射成像的重要一步。
英文摘要
The prospect of imaging single biomolecules, viruses and cells with intense, ultrashort X-ray pulses has driven the development of X-ray free-electron lasers (XFELs). However, the weak scattering from small particles is easily swamped by background from residual gas, which has so far limited applications to strongly scattering targets such as viruses, cell organelles and cells. Here we report a three-dimensional (3D) reconstruction of an isolated 1-MDa membrane-protein complex, photosystem I (PS I), from single-particle diffraction data. PS I trimers were aerosolised by charge-reduction electrospray ionisation and injected into the European XFEL beam, with partial helium gas exchange reducing background scattering by 80%. From 32 788 diffraction patterns of single trimers in random orientations, we reconstructed the 3D electron density to a resolution of 3.8 nm, limited by the detector geometry. The disc-shaped density, about 22 nm across and 10 nm thick, matches the size of a PS I trimer in a detergent micelle and is consistent with the compaction predicted by molecular dynamics simulations of the complex in vacuo and observed in native mass spectrometry. These results show that membrane-protein complexes can be imaged in vacuo with X-ray lasers, an important step towards ultrafast diffractive imaging of single macromolecules.
