Center for Free-Electron Laser Science, DESY, 22607 Hamburg, Germany; email:
Department of Physics, University of Hamburg, 22761 Hamburg, Germany.
Annu Rev Biochem. 2019 Jun 20;88:35-58. doi: 10.1146/annurev-biochem-013118-110744. Epub 2019 Jan 2.
X-ray free-electron lasers provide femtosecond-duration pulses of hard X-rays with a peak brightness approximately one billion times greater than is available at synchrotron radiation facilities. One motivation for the development of such X-ray sources was the proposal to obtain structures of macromolecules, macromolecular complexes, and virus particles, without the need for crystallization, through diffraction measurements of single noncrystalline objects. Initial explorations of this idea and of outrunning radiation damage with femtosecond pulses led to the development of serial crystallography and the ability to obtain high-resolution structures of small crystals without the need for cryogenic cooling. This technique allows the understanding of conformational dynamics and enzymatics and the resolution of intermediate states in reactions over timescales of 100 fs to minutes. The promise of more photons per atom recorded in a diffraction pattern than electrons per atom contributing to an electron micrograph may enable diffraction measurements of single molecules, although challenges remain.
X 射线自由电子激光提供了具有飞秒持续时间的硬 X 射线脉冲，其峰值亮度大约比同步辐射设施中可用的亮度高 10 亿倍。开发这种 X 射线源的一个动机是提出通过对单个非晶态物体的衍射测量来获得大分子、大分子复合物和病毒颗粒的结构，而无需结晶。最初对这一想法的探索以及利用飞秒脉冲超越辐射损伤，导致了连续晶体学的发展以及获得无需低温冷却的小晶体高分辨率结构的能力。该技术允许理解构象动力学和酶学，并在 100fs 到分钟的时间尺度内解决反应中的中间状态。与电子显微镜相比，在衍射图谱中记录的每个原子的更多光子可能会超过有助于电子显微镜的电子，这可能会使单个分子的衍射测量成为可能，尽管仍然存在挑战。
