Joint Laboratory for Structural Biology of Infection and Inflammation, Institute of Biochemistry and Molecular Biology, University of Hamburg and Institute of Biochemistry, University of Luebeck at DESY, 22607 Hamburg, Germany.
Photon Science, Deutsches Elektronen-Synchrotron DESY , Notkestrasse 85, 22607 Hamburg, Germany.
Struct Dyn. 2015 Apr 29;2(4):041703. doi: 10.1063/1.4919398. eCollection 2015 Jul.
Current hard X-ray free-electron laser (XFEL) sources can deliver doses to biological macromolecules well exceeding 1 GGy, in timescales of a few tens of femtoseconds. During the pulse, photoionization can reach the point of saturation in which certain atomic species in the sample lose most of their electrons. This electronic radiation damage causes the atomic scattering factors to change, affecting, in particular, the heavy atoms, due to their higher photoabsorption cross sections. Here, it is shown that experimental serial femtosecond crystallography data collected with an extremely bright XFEL source exhibit a reduction of the effective scattering power of the sulfur atoms in a native protein. Quantitative methods are developed to retrieve information on the effective ionization of the damaged atomic species from experimental data, and the implications of utilizing new phasing methods which can take advantage of this localized radiation damage are discussed.
目前的硬 X 射线自由电子激光（XFEL）源可以在几十飞秒的时间内将剂量输送到生物大分子，超过 1 戈瑞。在脉冲过程中，光致电离可以达到饱和点，此时样品中的某些原子物种会失去大部分电子。这种电子辐射损伤会导致原子散射因子发生变化，特别是由于较重原子的光吸收横截面较高，因此会影响重原子。本文表明，使用极其明亮的 XFEL 源收集的实验性连续飞秒晶体学数据显示，天然蛋白质中硫原子的有效散射能力降低。开发了定量方法，从实验数据中检索有关受损原子物种有效电离的信息，并讨论了利用可以利用这种局部辐射损伤的新相位方法的意义。
