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Instruments / Technical Area	Publication Details	Published
	Untangling the sequence of events during the S 2 → S 3 transition in photosystem II and implications for the water oxidation mechanism Mohamed Ibrahim , Thomas Fransson , Ruchira Chatterjee , Mun Hon Cheah , Rana Hussein , Louise Lassalle , Kyle D. Sutherlin , Iris D. Young , Franklin D. Fuller , Sheraz Gul , In-Sik Kim , Philipp S. Simon , Casper De Lichtenberg , Petko Chernev , Isabel Bogacz , Cindy C. Pham , Allen M. Orville , Nicholas Saichek , Trent Northen , Alexander Batyuk , Sergio Carbajo , Roberto Alonso-Mori , Kensuke Tono , Shigeki Owada , Asmit Bhowmick , Robert Bolotovsky , Derek Mendez , Nigel W. Moriarty , James M. Holton , Holger Dobbek , Aaron S. Brewster , Paul D. Adams , Nicholas K. Sauter , Uwe Bergmann , Athina Zouni , Johannes Messinger , Jan Kern , Vittal K. Yachandra , Junko Yano Proceedings Of The National Academy Of Sciences 766 DOI: 10.1073/pnas.2000529117 Open Access Show Abstract ▼ Abstract: In oxygenic photosynthesis, light-driven oxidation of water to molecular oxygen is carried out by the oxygen-evolving complex (OEC) in photosystem II (PS II). Recently, we reported the room-temperature structures of PS II in the four (semi)stable S-states, S1, S2, S3, and S0, showing that a water molecule is inserted during the S2 → S3 transition, as a new bridging O(H)-ligand between Mn1 and Ca. To understand the sequence of events leading to the formation of this last stable intermediate state before O2 formation, we recorded diffraction and Mn X-ray emission spectroscopy (XES) data at several time points during the S2 → S3 transition. At the electron acceptor site, changes due to the two-electron redox chemistry at the quinones, QA and QB, are observed. At the donor site, tyrosine YZ and His190 H-bonded to it move by 50 µs after the second flash, and Glu189 moves away from Ca. This is followed by Mn1 and Mn4 moving apart, and the insertion of OX(H) at the open coordination site of Mn1. This water, possibly a ligand of Ca, could be supplied via a “water wheel”-like arrangement of five waters next to the OEC that is connected by a large channel to the bulk solvent. XES spectra show that Mn oxidation (τ of ∼350 µs) during the S2 → S3 transition mirrors the appearance of OX electron density. This indicates that the oxidation state change and the insertion of water as a bridging atom between Mn1 and Ca are highly correlated.	May 2020
	Structures of the intermediates of Kok’s photosynthetic water oxidation clock Jan Kern , Ruchira Chatterjee , Iris D. Young , Franklin D. Fuller , Louise Lassalle , Mohamed Ibrahim , Sheraz Gul , Thomas Fransson , Aaron S. Brewster , Roberto Alonso-Mori , Rana Hussein , Miao Zhang , Lacey Douthit , Casper De Lichtenberg , Mun Hon Cheah , Dmitry Shevela , Julia Wersig , Ina Seuffert , Dimosthenis Sokaras , Ernest Pastor , Clemens Weninger , Thomas Kroll , Raymond G. Sierra , Pierre Aller , Agata Butryn , Allen M. Orville , Mengning Liang , Alexander Batyuk , Jason E. Koglin , Sergio Carbajo , Sébastien Boutet , Nigel W. Moriarty , James M. Holton , Holger Dobbek , Paul D. Adams , Uwe Bergmann , Nicholas K. Sauter , Athina Zouni , Johannes Messinger , Junko Yano , Vittal K. Yachandra Nature 11 DOI: 10.1038/s41586-018-0681-2 Show Abstract ▼ Abstract: Inspired by the period-four oscillation in flash-induced oxygen evolution of photosystem II discovered by Joliot in 1969, Kok performed additional experiments and proposed a five-state kinetic model for photosynthetic oxygen evolution, known as Kok’s S-state clock or cycle1,2. The model comprises four (meta)stable intermediates (S0, S1, S2 and S3) and one transient S4 state, which precedes dioxygen formation occurring in a concerted reaction from two water-derived oxygens bound at an oxo-bridged tetra manganese calcium (Mn4CaO5) cluster in the oxygen-evolving complex3,4,5,6,7. This reaction is coupled to the two-step reduction and protonation of the mobile plastoquinone QB at the acceptor side of PSII. Here, using serial femtosecond X-ray crystallography and simultaneous X-ray emission spectroscopy with multi-flash visible laser excitation at room temperature, we visualize all (meta)stable states of Kok’s cycle as high-resolution structures (2.04–2.08 Å). In addition, we report structures of two transient states at 150 and 400 µs, revealing notable structural changes including the binding of one additional ‘water’, Ox, during the S2→S3 state transition. Our results suggest that one water ligand to calcium (W3) is directly involved in substrate delivery. The binding of the additional oxygen Ox in the S3 state between Ca and Mn1 supports O–O bond formation mechanisms involving O5 as one substrate, where Ox is either the other substrate oxygen or is perfectly positioned to refill the O5 position during O2 release. Thus, our results exclude peroxo-bond formation in the S3 state, and the nucleophilic attack of W3 onto W2 is unlikely.	Nov 2018
	Drop-on-demand sample delivery for studying biocatalysts in action at X-ray free-electron lasers Franklin D Fuller , Sheraz Gul , Ruchira Chatterjee , E. Sethe Burgie , Iris D. Young , Hugo Lebrette , Vivek Srinivas , Aaron Brewster , Tara Michels-Clark , Jonathan A Clinger , Babak Andi , Mohamed Ibrahim , Ernest Pastor , Casper De Lichtenberg , Rana Hussein , Christopher J Pollock , Miao Zhang , Claudiu A Stan , Thomas Kroll , Thomas Fransson , Clemens Weninger , Markus Kubin , Pierre Aller , Louise Lassalle , Philipp Braeuer , Mitchell D. Miller , Muhamed Amin , Sergey Koroidov , Christian G. Roessler , Marc Allaire , Raymond G Sierra , Peter T. Docker , James M. Glownia , Silke Nelson , Jason E Koglin , Diling Zhu , Matthieu Chollet , Sanghoon Song , Henrik Lemke , Mengning Liang , Dimosthenis Sokaras , Roberto Alonso-Mori , Athina Zouni , Johannes Messinger , Uwe Bergmann , Amie K. Boal , J. Martin Bollinger , Carsten Krebs , Martin Högbom , George N. Phillips , Richard D. Vierstra , Nicholas K Sauter , Allen M. Orville , Jan Kern , Vittal K Yachandra , Junko Yano Nature Methods 5 DOI: 10.1038/nmeth.4195 Show Abstract ▼ Abstract: X-ray crystallography at X-ray free-electron laser sources is a powerful method for studying macromolecules at biologically relevant temperatures. Moreover, when combined with complementary techniques like X-ray emission spectroscopy, both global structures and chemical properties of metalloenzymes can be obtained concurrently, providing insights into the interplay between the protein structure and dynamics and the chemistry at an active site. The implementation of such a multimodal approach can be compromised by conflicting requirements to optimize each individual method. In particular, the method used for sample delivery greatly affects the data quality. We present here a robust way of delivering controlled sample amounts on demand using acoustic droplet ejection coupled with a conveyor belt drive that is optimized for crystallography and spectroscopy measurements of photochemical and chemical reactions over a wide range of time scales. Studies with photosystem II, the phytochrome photoreceptor, and ribonucleotide reductase R2 illustrate the power and versatility of this method.	Feb 2017
	Structure of photosystem II and substrate binding at room temperature Iris D. Young , Mohamed Ibrahim , Ruchira Chatterjee , Sheraz Gul , Franklin D. Fuller , Sergey Koroidov , Aaron S. Brewster , Rosalie Tran , Roberto Alonso-Mori , Thomas Kroll , Tara Michels-Clark , Hartawan Laksmono , Raymond G. Sierra , Claudiu A. Stan , Rana Hussein , Miao Zhang , Lacey Douthit , Markus Kubin , Casper De Lichtenberg , Long Vo Pham , Håkan Nilsson , Mun Hon Cheah , Dmitriy Shevela , Claudio Saracini , Mackenzie A. Bean , Ina Seuffert , Dimosthenis Sokaras , Tsu-Chien Weng , Ernest Pastor , Clemens Weninger , Thomas Fransson , Louise Lassalle , Philipp Bräuer , Pierre Aller , Peter T. Docker , Babak Andi , Allen M. Orville , James M. Glownia , Silke Nelson , Marcin Sikorski , Diling Zhu , Mark S. Hunter , Thomas J. Lane , Andy Aquila , Jason E. Koglin , Joseph Robinson , Mengning Liang , Sébastien Boutet , Artem Y. Lyubimov , Monarin Uervirojnangkoorn , Nigel W. Moriarty , Dorothee Liebschner , Pavel V. Afonine , David G. Waterman , Gwyndaf Evans , Philippe Wernet , Holger Dobbek , William I. Weis , Axel T. Brunger , Petrus H. Zwart , Paul D. Adams , Athina Zouni , Johannes Messinger , Uwe Bergmann , Nicholas K. Sauter , Jan Kern , Vittal K. Yachandra , Junko Yano Nature DOI: 10.1038/nature20161 Show Abstract ▼ Abstract: Light-induced oxidation of water by photosystem II (PS II) in plants, algae and cyanobacteria has generated most of the dioxygen in the atmosphere. PS II, a membrane-bound multi-subunit pigment protein complex, couples the one-electron photochemistry at the reaction centre with the four-electron redox chemistry of water oxidation at the Mn4CaO5 cluster in the oxygen-evolving complex (OEC). Under illumination, the OEC cycles through five intermediate S-states (S0 to S4)1, in which S1 is the dark-stable state and S3 is the last semi-stable state before O–O bond formation and O2 evolution2, 3. A detailed understanding of the O–O bond formation mechanism remains a challenge, and will require elucidation of both the structures of the OEC in the different S-states and the binding of the two substrate waters to the catalytic site4, 5, 6. Here we report the use of femtosecond pulses from an X-ray free electron laser (XFEL) to obtain damage-free, room temperature structures of dark-adapted (S1), two-flash illuminated (2F; S3-enriched), and ammonia-bound two-flash illuminated (2F-NH3; S3-enriched) PS II. Although the recent 1.95 Å resolution structure of PS II at cryogenic temperature using an XFEL7 provided a damage-free view of the S1 state, measurements at room temperature are required to study the structural landscape of proteins under functional conditions8, 9, and also for in situ advancement of the S-states. To investigate the water-binding site(s), ammonia, a water analogue, has been used as a marker, as it binds to the Mn4CaO5 cluster in the S2 and S3 states10. Since the ammonia-bound OEC is active, the ammonia-binding Mn site is not a substrate water site10, 11, 12, 13. This approach, together with a comparison of the native dark and 2F states, is used to discriminate between proposed O–O bond formation mechanisms.	Nov 2016
I04-1-Macromolecular Crystallography (fixed wavelength) I24-Microfocus Macromolecular Crystallography	Fast high-pressure freezing of protein crystals in their mother liquor Anja Burkhardt , Martin Warmer , Saravanan Panneerselvam , Armin Wagner , Athina Zouni , Carina Gloeckner , Rudolph Reimer , Heinrich Hohenberg , Alke Meents Acta Crystallographica Section F Structural Biology And Crystallization Communications 68 (4), 495-500 DOI: 10.1107/S1744309112009670 PMID: 22505429 Show Abstract ▼ Abstract: High-pressure freezing (HPF) is a method which allows sample vitrification without cryoprotectants. In the present work, protein crystals were cooled to cryogenic temperatures at a pressure of 210 MPa. In contrast to other HPF methods published to date in the field of cryocrystallography, this protocol involves rapid sample cooling using a standard HPF device. The fast cooling rates allow HPF of protein crystals directly in their mother liquor without the need for cryoprotectants or external reagents. HPF was first attempted with hen egg-white lysozyme and cubic insulin crystals, yielding good to excellent diffraction quality. Non-cryoprotected crystals of the membrane protein photosystem II have been successfully cryocooled for the first time. This indicates that the presented HPF method is well suited to the vitrification of challenging systems with large unit cells and weak crystal contacts.	Apr 2012

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