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Published September 2017 | Published + Supplemental Material
Journal Article Open

Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers


X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. However, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties. We present L-edge absorption spectra of inorganic high-valent Mn complexes (Mn ∼ 6–15 mmol/l) with no visible effects of radiation damage. We also present the first L-edge absorption spectra of the oxygen evolving complex (Mn_4CaO_5) in Photosystem II (Mn < 1 mmol/l) at room temperature, measured under similar conditions. Our approach opens new ways to study metalloenzymes under functional conditions.

Additional Information

© 2017 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). Received 6 June 2017; accepted 15 August 2017; published online 1 September 2017. This work was supported by the Director, Office of Science, Office of Basic Energy Sciences (OBES), Division of Chemical Sciences, Geosciences, and Biosciences (CSGB) of the Department of Energy (DOE) under contract DE-AC02-05CH11231 (J.Y. and V.K.Y.) for X-ray methodology and instrumentation, the National Institutes of Health (NIH) under Grant Nos. GM110501 (J.Y.) for instrumentation development for XFEL experiments and GM055302 (V.K.Y.) for PS II biochemistry, structure, and mechanism, the Ruth L. Kirschstein National Research Service Award (5 F32 GM116423‐02, F.D.F.), the Human Frontiers Science under Project Award No. RGP0063/2013 310 (J.Y., U.B., and Ph. W.), the K&A Wallenberg foundation (J.M., Grant No. 2011.0055), Energimyndigheten (J.M., Grant No. 36648‐1), Vetenskapsrådet (J.M., Grant No. 2016‐05183), and the Helmholtz Virtual Institute "Dynamic Pathways in Multidimensional Landscapes." The SSRL Structural Molecular Biology Program (T.K.) was supported by the DOE Office of Biological and Environmental Research and by the National Institutes of Health, National Institute of General Medical Sciences (including P41GM103393). This research was carried out on the SXR Instrument at the Linac Coherent Light Source (LCLS), a division of SLAC National Accelerator Laboratory and an Office of Science user facility operated by Stanford University for the U.S. Department of Energy. The SXR Instrument was funded by a consortium whose membership includes the LCLS, Stanford University, through the Stanford Institute for Materials Energy Sciences (SIMES), Lawrence Berkeley National Laboratory (LBNL), University of Hamburg through the BMBF priority program FSP 301, and the Center for Free Electron Laser Science (CFEL). NIH (R01-GM102687A) is acknowledged for supporting the synthesis of model cluster complexes (T.A.). We would like to acknowledge the Swedish Research Council for supporting the theoretical efforts discussed here. We would like to thank the staff at the SXR beam line for their support in this experiment and Dan DePonte and the Sample Environment Department at LCLS for providing the GDVN nozzles and support for the injection of the model compounds.

Attached Files

Published - 1_2E4986627.pdf

Supplemental Material - psii_l-edge_6_june_17_suppinfo.pdf


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August 19, 2023
October 17, 2023