Poudyal I, Schmidt M, Schwander P
Department of Physics, University of Wisconsin-Milwaukee, 3135 N. Maryland Ave., Milwaukee, Wisconsin 53211, USA.
Struct Dyn. 2020 Mar 20;7(2):024102. doi: 10.1063/1.5144516. eCollection 2020 Mar.
X-ray free-electron lasers (XFELs) open the possibility of obtaining diffraction information from a single biological macromolecule. This is because XFELs can generate extremely intense x-ray pulses that are so short that diffraction data can be collected before the sample is destroyed. By collecting a sufficient number of single-particle diffraction patterns, the three-dimensional electron density of a molecule can be reconstructed . The quality of the reconstruction depends largely on the number of patterns collected at the experiment. This paper provides an estimate of the number of diffraction patterns required to reconstruct the electron density at a targeted spatial resolution. This estimate is verified by simulations for realistic x-ray fluences, repetition rates, and experimental conditions available at modern XFELs. Employing the bacterial phytochrome as a model system, we demonstrate that sub-nanometer resolution is within reach.
X射线自由电子激光（XFEL）开启了从单个生物大分子获取衍射信息的可能性。这是因为XFEL能够产生极其强烈的X射线脉冲，其脉冲持续时间极短，以至于可以在样品被破坏之前收集衍射数据。通过收集足够数量的单粒子衍射图样，可以重建分子的三维电子密度。重建的质量在很大程度上取决于实验中收集的图样数量。本文提供了在目标空间分辨率下重建电子密度所需衍射图样数量的估计。该估计通过针对现代XFEL现有的实际X射线通量、重复率和实验条件进行的模拟得到验证。以细菌光敏色素作为模型系统，我们证明亚纳米分辨率是可以实现的。
