Barends Thomas R M, Foucar Lutz, Shoeman Robert L, Bari Sadia, Epp Sascha W, Hartmann Robert, Hauser Gunter, Huth Martin, Kieser Christian, Lomb Lukas, Motomura Koji, Nagaya Kiyonobu, Schmidt Carlo, Strecker Rafael, Anielski Denis, Boll Rebecca, Erk Benjamin, Fukuzawa Hironobu, Hartmann Elisabeth, Hatsui Takaki, Holl Peter, Inubushi Yuichi, Ishikawa Tetsuya, Kassemeyer Stephan, Kaiser Christian, Koeck Frank, Kunishima Naoki, Kurka Moritz, Rolles Daniel, Rudek Benedikt, Rudenko Artem, Sato Takahiro, Schroeter Claus Dieter, Soltau Heike, Strueder Lothar, Tanaka Tomoyuki, Togashi Tadashi, Tono Kensuke, Ullrich Joachim, Yase Satoshi, Wada Shin Ichi, Yao Makoto, Yabashi Makina, Ueda Kiyoshi, Schlichting Ilme
Max-Planck-Institut für medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany.
Acta Crystallogr D Biol Crystallogr. 2013 May;69(Pt 5):838-42. doi: 10.1107/S0907444913002448. Epub 2013 Apr 11.
X-ray free-electron lasers (FELs) enable crystallographic data collection using extremely bright femtosecond pulses from microscopic crystals beyond the limitations of conventional radiation damage. This diffraction-before-destruction approach requires a new crystal for each FEL shot and, since the crystals cannot be rotated during the X-ray pulse, data collection requires averaging over many different crystals and a Monte Carlo integration of the diffraction intensities, making the accurate determination of structure factors challenging. To investigate whether sufficient accuracy can be attained for the measurement of anomalous signal, a large data set was collected from lysozyme microcrystals at the newly established `multi-purpose spectroscopy/imaging instrument' of the SPring-8 Ångstrom Compact Free-Electron Laser (SACLA) at RIKEN Harima. Anomalous difference density maps calculated from these data demonstrate that serial femtosecond crystallography using a free-electron laser is sufficiently accurate to measure even the very weak anomalous signal of naturally occurring S atoms in a protein at a photon energy of 7.3 keV.
X射线自由电子激光（FEL）能够利用来自微观晶体的极亮飞秒脉冲进行晶体学数据收集，突破了传统辐射损伤的限制。这种“破坏前衍射”方法每次FEL照射都需要一块新晶体，而且由于在X射线脉冲期间晶体无法旋转，数据收集需要对许多不同晶体进行平均，并对衍射强度进行蒙特卡罗积分，这使得准确确定结构因子具有挑战性。为了研究在测量反常信号时是否能够达到足够的精度，在位于日本理化学研究所播磨的SPring-8埃紧凑型自由电子激光（SACLA）新建成的“多功能光谱/成像仪”上，从溶菌酶微晶中收集了一个大数据集。根据这些数据计算出的反常差异密度图表明，使用自由电子激光的串行飞秒晶体学足够精确，甚至能够在7.3 keV的光子能量下测量蛋白质中天然存在的S原子的非常微弱的反常信号。
