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Structural dynamics in proteins induced by and probed with X-ray free-electron laser pulses
Karol Nass (Max Planck Institute for Medical Research), A. Gorel (Max Planck Institute for Medical Research), Malik Muhammad Abdullah (Deutsches Elektronen-Synchrotron DESY, Center for Free-Electron Laser Science), Andrew V. Martin (RMIT University), Marco Kloos (Max Planck Institute for Medical Research), Agostino Marinelli (SLAC National Accelerator Laboratory), Andrew Aquila (SLAC National Accelerator Laboratory), Thomas R. M. Barends (Max Planck Institute for Medical Research), F.-J. Decker (SLAC National Accelerator Laboratory), R. Bruce Doak (Max Planck Institute for Medical Research), L. Foucar (Max Planck Institute for Medical Research), Elisabeth Hartmann (Max Planck Institute for Medical Research), M. Hilpert (Max Planck Institute for Medical Research), Mark S. Hunter (SLAC National Accelerator Laboratory), Zoltán Jurek (Deutsches Elektronen-Synchrotron DESY, Center for Free-Electron Laser Science), Jason E. Koglin (SLAC National Accelerator Laboratory), Alexander Kozlov (The University of Melbourne, ARC Centre of Excellence in Advanced Molecular Imaging), Alberto A. Lutman (SLAC National Accelerator Laboratory), Gabriela Nass Kovacs (Max Planck Institute for Medical Research), Christopher M. Roome (Max Planck Institute for Medical Research), Robert L. Shoeman (Max Planck Institute for Medical Research), Robin Santra (Universität Hamburg, Deutsches Elektronen-Synchrotron DESY), Harry M. Quiney (The University of Melbourne, ARC Centre of Excellence in Advanced Molecular Imaging), Beata Ziaja (Deutsches Elektronen-Synchrotron DESY, Institute of Nuclear Physics, Polish Academy of Sciences), Sébastien Boutet (SLAC National Accelerator Laboratory), Ilme Schlichting (Max Planck Institute for Medical Research)
Résumé : X-ray free-electron lasers (XFELs) enable crystallographic structure determination beyond the limitations imposed upon synchrotron measurements by radiation damage. The need for very short XFEL pulses is relieved through gating of Bragg diffraction by loss of crystalline order as damage progresses, but not if ionization events are spatially non-uniform due to underlying elemental distributions, as in biological samples. Indeed, correlated movements of iron and sulfur ions were observed in XFEL-irradiated ferredoxin microcrystals using unusually long pulses of 80 fs. Here, we report a femtosecond time-resolved X-ray pump/X-ray probe experiment on protein nanocrystals. We observe changes in the protein backbone and aromatic residues as well as disulfide bridges. Simulations show that the latter's correlated structural dynamics are much slower than expected for the predicted high atomic charge states due to significant impact of ion caging and plasma electron screening. This indicates that dense-environment effects can strongly affect local radiation damage-induced structural dynamics.