MS03-P04 Simultaneous XRD and XES at XFELs, elucidating electronic and geometric structures of metalloproteins Roberto Alonso Mori (SLAC National Accelerator Laboratory, Menlo Park, United States of America)email: robertoa@slac.stanford.eduOne of the fields where the advantages of X-ray free electron lasers (XFELs) have proven to be very fruitful is in the study of metalloproteins(1). These proteins, where metal centers efficiently catalyze chemical processes under ambient conditions, are ubiquitous in nature. X-Ray diffraction (XRD) has become a standard technique in synchrotron radiation (SR) sources worldwide to elucidate the geometric structure of crystallized proteins, and X-ray spectroscopic techniques to provide information about the electronic structure of the active site. Despite the enormous progress of the field achieved from SR-based measurements, these studies suffer from some experimental constraints, the main being the radiation-induced damage of the sample by the X-rays, which makes it difficult to collect the signal from the intact sample for radiation-sensitive systems.
At XFELs, each fs X-ray pulse is short enough to probe the sample and yield a detectable signal outrunning the SR-type radiation damage (in the ps) scale. The consequence is the possibility to measure sensitive systems under ambient, and therefore, functional conditions. The short X-ray pulses also allow the study of these processes in real time by following the catalytic reactions and the associated electronic and geometric changes step by step with fs time resolution. In this presentation I will describe the methods developed in the past few years at XFELs to study metalloproteins and discuss some examples and applications. In particular I will emphasize how X-ray emission spectroscopy can be used as an in situ method for monitoring the integrity of metal catalytic centers during simultaneous XRD data collection(2).

1-R. Alonso-Mori and J. Kern. (2017) “X-ray Free Electron Lasers”. Chapter VII “Damage-Free Electronic and Geometric Structure Determination of Metalloproteins”. Royal Society of Chemistry

2-R. Alonso-Mori, J. Kern, R.J. Gildea et al. (2012) “Energy-Dispersive X-ray Emission Spectroscopy Using an X-ray Free Electron Laser In a Shot-by-Shot mode”. Proc. Natl. Acad. Sci. U.S.A. 109, 19103-19107

Keywords: XES, Spectroscopy, XFEL