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  • 1. Alonso-Mori, R.
    et al.
    Asa, K.
    Bergmann, U.
    Brewster, A. S.
    Chatterjee, R.
    Cooper, J. K.
    Frei, H. M.
    Fuller, F. D.
    Goggins, E.
    Gul, S.
    Fukuzawa, H.
    Iablonskyi, D.
    Ibrahim, M.
    Katayama, T.
    Kroll, T.
    Kumagai, Y.
    McClure, B. A.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Motomura, K.
    Nagaya, K.
    Nishiyama, T.
    Saracini, C.
    Sato, Y.
    Sauter, N. K.
    Sokaras, D.
    Takanashi, T.
    Togashi, T.
    Ueda, K.
    Weare, W. W.
    Weng, T-C
    Yabashi, M.
    Yachandra, V. K.
    Young, I. D.
    Zouni, A.
    Kern, J. F.
    Yano, J.
    Towards characterization of photo-excited electron transfer and catalysis in natural and artificial systems using XFELs2016In: Faraday discussions (Online), ISSN 1359-6640, E-ISSN 1364-5498, Vol. 194, p. 621-638Article in journal (Refereed)
    Abstract [en]

    The ultra-bright femtosecond X-ray pulses provided by X-ray Free Electron Lasers (XFELs) open capabilities for studying the structure and dynamics of a wide variety of biological and inorganic systems beyond what is possible at synchrotron sources. Although the structure and chemistry at the catalytic sites have been studied intensively in both biological and inorganic systems, a full understanding of the atomic-scale chemistry requires new approaches beyond the steady state X-ray crystallography and X-ray spectroscopy at cryogenic temperatures. Following the dynamic changes in the geometric and electronic structure at ambient conditions, while overcoming X-ray damage to the redox active catalytic center, is key for deriving reaction mechanisms. Such studies become possible by using the intense and ultra-short femtosecond X-ray pulses from an XFEL, where sample is probed before it is damaged. We have developed methodology for simultaneously collecting X-ray diffraction data and X-ray emission spectra, using an energy dispersive spectrometer, at ambient conditions, and used this approach to study the room temperature structure and intermediate states of the photosynthetic water oxidizing metallo-protein, photosystem II. Moreover, we have also used this setup to simultaneously collect the X-ray emission spectra from multiple metals to follow the ultrafast dynamics of light-induced charge transfer between multiple metal sites. A Mn-Ti containing system was studied at an XFEL to demonstrate the efficacy and potential of this method.

  • 2. Alonso-Mori, Roberto
    et al.
    Kern, Jan
    Gildea, Richard J
    Sokaras, Dimosthenis
    Weng, Tsu-Chien
    Lassalle-Kaiser, Benedikt
    Tran, Rosalie
    Hattne, Johan
    Laksmono, Hartawan
    Hellmich, Julia
    Glöckner, Carina
    Echols, Nathaniel
    Sierra, Raymond G
    Schafer, Donald W
    Sellberg, Jonas
    Kenney, Christopher
    Herbst, Ryan
    Pines, Jack
    Hart, Philip
    Herrmann, Sven
    Grosse-Kunstleve, Ralf W
    Latimer, Matthew J
    Fry, Alan R
    Messerschmidt, Marc M
    Miahnahri, Alan
    Seibert, M Marvin
    Zwart, Petrus H
    White, William E
    Adams, Paul D
    Bogan, Michael J
    Boutet, Sébastien
    Williams, Garth J
    Zouni, Athina
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Glatzel, Pieter
    Sauter, Nicholas K
    Yachandra, Vittal K
    Yano, Junko
    Bergmann, Uwe
    Energy-dispersive X-ray emission spectroscopy using an X-ray free-electron laser in a shot-by-shot mode2012In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 47, p. 19103-19107Article in journal (Refereed)
    Abstract [en]

    The ultrabright femtosecond X-ray pulses provided by X-ray free-electron lasers open capabilities for studying the structure and dynamics of a wide variety of systems beyond what is possible with synchrotron sources. Recently, this "probe-before-destroy" approach has been demonstrated for atomic structure determination by serial X-ray diffraction of microcrystals. There has been the question whether a similar approach can be extended to probe the local electronic structure by X-ray spectroscopy. To address this, we have carried out femtosecond X-ray emission spectroscopy (XES) at the Linac Coherent Light Source using redox-active Mn complexes. XES probes the charge and spin states as well as the ligand environment, critical for understanding the functional role of redox-active metal sites. Kβ(1,3) XES spectra of Mn(II) and Mn(2)(III,IV) complexes at room temperature were collected using a wavelength dispersive spectrometer and femtosecond X-ray pulses with an individual dose of up to >100 MGy. The spectra were found in agreement with undamaged spectra collected at low dose using synchrotron radiation. Our results demonstrate that the intact electronic structure of redox active transition metal compounds in different oxidation states can be characterized with this shot-by-shot method. This opens the door for studying the chemical dynamics of metal catalytic sites by following reactions under functional conditions. The technique can be combined with X-ray diffraction to simultaneously obtain the geometric structure of the overall protein and the local chemistry of active metal sites and is expected to prove valuable for understanding the mechanism of important metalloproteins, such as photosystem II.

  • 3. Ames, William
    et al.
    Pantazis, Dimitrios A
    Krewald, Vera
    Cox, Nicholas
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lubitz, Wolfgang
    Neese, Frank
    Theoretical Evaluation of Structural Models of the S(2) State in the Oxygen Evolving Complex of Photosystem II: Protonation States and Magnetic Interactions2011In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, no 49, p. 19743-19757Article in journal (Refereed)
    Abstract [en]

    Protonation states of water ligands and oxo bridges are intimately involved in tuning the electronic structures and oxidation potentials of the oxygen evolving complex (OEC) in Photosystem II, steering the mechanistic pathway, which involves at least five redox state intermediates S(n) (n = 0-4) resulting in the oxidation of water to molecular oxygen. Although protons are practically invisible in protein crystallography, their effects on the electronic structure and magnetic properties of metal active sites can be probed using spectroscopy. With the twin purpose of aiding the interpretation of the complex electron paramagnetic resonance (EPR) spectroscopic data of the OEC and of improving the view of the cluster at the atomic level, a complete set of protonation configurations for the S(2) state of the OEC were investigated, and their distinctive effects on magnetic properties of the cluster were evaluated. The most recent X-ray structure of Photosystem II at 1.9 Å resolution was used and refined to obtain the optimum structure for the Mn(4)O(5)Ca core within the protein pocket. Employing this model, a set of 26 structures was constructed that tested various protonation scenarios of the water ligands and oxo bridges. Our results suggest that one of the two water molecules that are proposed to coordinate the outer Mn ion (Mn(A)) of the cluster is deprotonated in the S(2) state, as this leads to optimal experimental agreement, reproducing the correct ground state spin multiplicity (S = 1/2), spin expectation values, and EXAFS-derived metal-metal distances. Deprotonation of Ca(2+)-bound water molecules is strongly disfavored in the S(2) state, but dissociation of one of the two water ligands appears to be facile. The computed isotropic hyperfine couplings presented here allow distinctions between models to be made and call into question the assumption that the largest coupling is always attributable to Mn(III). The present results impose limits for the total charge and the proton configuration of the OEC in the S(2) state, with implications for the cascade of events in the Kok cycle and for the water splitting mechanism.

  • 4. Arafa, Wael A. A.
    et al.
    Kärkäs, Markus D.
    Lee, Bao-Lin
    Åkermark, Torbjörn
    Liao, Rong-Zhen
    Berends, Hans-Martin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Siegbahn, Per E. M.
    Åkermark, Björn
    Dinuclear manganese complexes for water oxidation: evaluation of electronic effects and catalytic activity2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 24, p. 11950-11964Article in journal (Refereed)
    Abstract [en]

    During recent years significant progress has been made towards the realization of a sustainable and carbon-neutral energy economy. One promising approach is photochemical splitting of H2O into O-2 and solar fuels, such as H-2. However, the bottleneck in such artificial photosynthetic schemes is the H2O oxidation half reaction where more efficient catalysts are required that lower the kinetic barrier for this process. In particular catalysts based on earth-abundant metals are highly attractive compared to catalysts comprised of noble metals. We have now synthesized a library of dinuclear Mn-2 (II,III) catalysts for H2O oxidation and studied how the incorporation of different substituents affected the electronics and catalytic efficiency. It was found that the incorporation of a distal carboxyl group into the ligand scaffold resulted in a catalyst with increased catalytic activity, most likely because of the fact that the distal group is able to promote proton-coupled electron transfer (PCET) from the high-valent Mn species, thus facilitating O-O bond formation.

  • 5.
    Beckmann, Katrin
    et al.
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Badger, Murray Ronald
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Wydrzynski, Tom
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    Hillier, Warwick
    School of Biology, Australian National University, Canberra, ACT 0200 Australia.
    On-line mass spectrometry: membrane inlet sampling2009In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 102, no 2-3, p. 511-522Article in journal (Refereed)
    Abstract [en]

    Significant insights into plant photosynthesis and respiration have been achieved using membrane inlet mass spectrometry (MIMS) for the analysis of stable isotope distribution of gases. The MIMS approach is based on using a gas permeable membrane to enable the entry of gas molecules into the mass spectrometer source. This is a simple yet durable approach for the analysis of volatile gases, particularly atmospheric gases. The MIMS technique strongly lends itself to the study of reaction flux where isotopic labeling is employed to differentiate two competing processes; i.e., O2 evolution versus O2 uptake reactions from PSII or terminal oxidase/rubisco reactions. Such investigations have been used for in vitro studies of whole leaves and isolated cells. The MIMS approach is also able to follow rates of isotopic exchange, which is useful for obtaining chemical exchange rates. These types of measurements have been employed for oxygen ligand exchange in PSII and to discern reaction rates of the carbonic anhydrase reactions. Recent developments have also engaged MIMS for online isotopic fractionation and for the study of reactions in inorganic systems that are capable of water splitting or H2 generation. The simplicity of the sampling approach coupled to the high sensitivity of modern instrumentation is a reason for the growing applicability of this technique for a range of problems in plant photosynthesis and respiration. This review offers some insights into the sampling approaches and the experiments that have been conducted with MIMS.

  • 6. Beckmann, Katrin
    et al.
    Uchtenhagen, Hannes
    Berggren, Gustav
    Anderlund, Magnus F
    Thapper, Anders
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Chemistry.
    Styring Stenbjörn,,
    Kurz Philipp,
    Formation of stoichiometrically 18O-labelled oxygen from the oxidation of 18O-enriched water mediated by a dinuclear manganese complex-a mass spectrometry and EPR study2008In: Energy & Environmental Science, Vol. 1, p. 668-76Article in journal (Refereed)
    Abstract [en]

    Oxygen formation was detected for the oxidations of various multinuclear manganese complexes by oxone (HSO5-) in aqueous solution. To determine to what extent water was the source of the evolved O2, H218O isotope-labelling experiments coupled with membrane inlet mass spectrometry (MIMS) were carried out. We discovered that during the reaction of oxone with [Mn2(OAc)2(bpmp)]+ (1), stoichiometrically labelled oxygen (18O2) was formed. This is the first example of a homogeneous reaction mediated by a synthetic manganese complex where the addition of a strong chemical oxidant yields 18O2 with labelling percentages matching the theoretically expected values for the case of both O-atoms originating from water. Experiments using lead acetate as an alternative oxidant supported this finding. A detailed investigation of the reaction by EPR spectroscopy, MIMS and Clark-type oxygen detection enabled us to propose potential reaction pathways.

  • 7.
    Benlloch, Reyes
    et al.
    Department of Forest Genetics and Plant Physiology, SLU.
    Shevela, Dmitriy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hainzl, Tobias
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Grundström, Christin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shutova, Tatyana
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Sauer-Eriksson, Elisabeth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Crystal structure and functional characterization of Photosystem II-associated carbonic anhydrase CAH3 in Chlamydomonas reinhardtii2015In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 167, no 3, p. 950-962Article in journal (Refereed)
    Abstract [en]

    In oxygenic photosynthesis, light energy is stored in the form of chemical energy by converting CO2 and water into carbohydrates.The light-driven oxidation of water that provides the electrons and protons for the subsequent CO2 fixation takes place inphotosystem II (PSII). Recent studies show that in higher plants, HCO3– increases PSII activity by acting as a mobile acceptor ofthe protons produced by PSII. In the green alga Chlamydomonas reinhardtii, a luminal carbonic anhydrase, CrCAH3, was suggested toimprove proton removal from PSII, possibly by rapid reformation of HCO3– from CO2. In this study, we investigated the interplaybetween PSII and CrCAH3 by membrane inlet mass spectrometry and x-ray crystallography. Membrane inlet mass spectrometrymeasurements showed that CrCAH3 was most active at the slightly acidic pH values prevalent in the thylakoid lumen underillumination. Two crystal structures of CrCAH3 in complex with either acetazolamide or phosphate ions were determined at 2.6- and2.7-Å resolution, respectively. CrCAH3 is a dimer at pH 4.1 that is stabilized by swapping of the N-terminal arms, a feature notpreviously observed in a-type carbonic anhydrases. The structure contains a disulfide bond, and redox titration of CrCAH3 functionwith dithiothreitol suggested a possible redox regulation of the enzyme. The stimulating effect of CrCAH3 and CO2/HCO3– on PSIIactivity was demonstrated by comparing the flash-induced oxygen evolution pattern of wild-type and CrCAH3-less PSIIpreparations. We showed that CrCAH3 has unique structural features that allow this enzyme to maximize PSII activity at lowpH and CO2 concentration.

  • 8.
    Burén, Stefan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Ortega-Villasante, Cristina
    Blanco-Rivero, Amaya
    Martínez-Bernardini, Andrea
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Shutova, Tatiana
    Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC). Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Shevela, Dmitriy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Bako, Laszlo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Villarejo, Arsenio
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Importance of post-translational modifications for functionality of a chloroplast-localized carbonic anhydrase (CAH1) in Arabidopsis thaliana2011In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 6, no 6, p. e21021-Article in journal (Refereed)
    Abstract [en]

    Background

    The Arabidopsis CAH1 alpha-type carbonic anhydrase is one of the few plant proteins known to be targeted to the chloroplast through the secretory pathway. CAH1 is post-translationally modified at several residues by the attachment of N-glycans, resulting in a mature protein harbouring complex-type glycans. The reason of why trafficking through this non-canonical pathway is beneficial for certain chloroplast resident proteins is not yet known. Therefore, to elucidate the significance of glycosylation in trafficking and the effect of glycosylation on the stability and function of the protein, epitope-labelled wild type and mutated versions of CAH1 were expressed in plant cells.

    Methodology/Principal Findings

    Transient expression of mutant CAH1 with disrupted glycosylation sites showed that the protein harbours four, or in certain cases five, N-glycans. While the wild type protein trafficked through the secretory pathway to the chloroplast, the non-glycosylated protein formed aggregates and associated with the ER chaperone BiP, indicating that glycosylation of CAH1 facilitates folding and ER-export. Using cysteine mutants we also assessed the role of disulphide bridge formation in the folding and stability of CAH1. We found that a disulphide bridge between cysteines at positions 27 and 191 in the mature protein was required for correct folding of the protein. Using a mass spectrometric approach we were able to measure the enzymatic activity of CAH1 protein. Under circumstances where protein N-glycosylation is blocked in vivo, the activity of CAH1 is completely inhibited.

    Conclusions/Significance

    We show for the first time the importance of post-translational modifications such as N-glycosylation and intramolecular disulphide bridge formation in folding and trafficking of a protein from the secretory pathway to the chloroplast in higher plants. Requirements for these post-translational modifications for a fully functional native protein explain the need for an alternative route to the chloroplast.

  • 9. Chatterjee, Ruchira
    et al.
    Lassalle, Louise
    Gul, Sheraz
    Fuller, Franklin D.
    Young, Iris D.
    Ibrahim, Mohamed
    de Lichtenberg, Casper
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry – Ångström, Molecular Biomimetics, Uppsala University, Uppsala 75237, Sweden.
    Cheah, Mun Hon
    Zouni, Athina
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry – Ångström, Molecular Biomimetics, Uppsala University, Uppsala 75237, Sweden.
    Yachandra, Vittal K.
    Kern, Jan
    Yano, Junko
    Structural isomers of the S-2 state in photosystem II: do they exist at room temperature and are they important for function?2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 166, no 1, p. 60-72Article in journal (Refereed)
    Abstract [en]

    In nature, an oxo‐bridged Mn4CaO5 cluster embedded in photosystem II (PSII), a membrane‐bound multi‐subunit pigment protein complex, catalyzes the water oxidation reaction that is driven by light‐induced charge separations in the reaction center of PSII. The Mn4CaO5 cluster accumulates four oxidizing equivalents to enable the four‐electron four‐proton catalysis of two water molecules to one dioxygen molecule and cycles through five intermediate S‐states, S0 – S4 in the Kok cycle. One important question related to the catalytic mechanism of the oxygen‐evolving complex (OEC) that remains is, whether structural isomers are present in some of the intermediate S‐states and if such equilibria are essential for the mechanism of the O‐O bond formation. Here we compare results from electron paramagnetic resonance (EPR) and X‐ray absorption spectroscopy (XAS) obtained at cryogenic temperatures for the S2state of PSII with structural data collected of the S1, S2 and S3 states by serial crystallography at neutral pH (∼6.5) using an X‐ray free electron laser at room temperature. While the cryogenic data show the presence of at least two structural forms of the S2 state, the room temperature crystallography data can be well‐described by just one S2 structure. We discuss the deviating results and outline experimental strategies for clarifying this mechanistically important question.

  • 10. Christianson, Helena C.
    et al.
    Menard, Julien A.
    Chandran, Vineesh Indira
    Bourseau-Guilmain, Erika
    Shevela, Dmitry
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lidfeldt, Jon
    Mansson, Ann-Sofie
    Pastorekova, Silvia
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Skane Univ Hosp, Lund, Sweden.
    Belting, Mattias
    Tumor antigen glycosaminoglycan modification regulates antibody-drug conjugate delivery and cytotoxicity2017In: OncoTarget, ISSN 1949-2553, E-ISSN 1949-2553, Vol. 8, no 40, p. 66960-66974Article in journal (Refereed)
    Abstract [en]

    Aggressive cancers are characterized by hypoxia, which is a key driver of tumor development and treatment resistance. Proteins specifically expressed in the hypoxic tumor microenvironment thus represent interesting candidates for targeted drug delivery strategies. Carbonic anhydrase (CAIX) has been identified as an attractive treatment target as it is highly hypoxia specific and expressed at the cell-surface to promote cancer cell aggressiveness. Here, we find that cancer cell internalization of CAIX is negatively regulated by post-translational modification with chondroitin or heparan sulfate glycosaminoglycan chains. We show that perturbed glycosaminoglycan modification results in increased CAIX endocytosis. We hypothesized that perturbation of CAIX glycosaminoglycan conjugation may provide opportunities for enhanced drug delivery to hypoxic tumor cells. In support of this concept, pharmacological inhibition of glycosaminoglycan biosynthesis with xylosides significantly potentiated the internalization and cytotoxic activity of an antibody-drug conjugate (ADC) targeted at CAIX. Moreover, cells expressing glycosaminoglycan-deficient CAIX were significantly more sensitive to ADC treatment as compared with cells expressing wild-type CAIX. We find that inhibition of CAIX endocytosis is associated with an increased localization of glycosaminoglycan-conjugated CAIX in membrane lipid raft domains stabilized by caveolin-1 clusters. The association of CAIX with caveolin-1 was partially attenuated by acidosis, i.e. another important feature of malignant tumors. Accordingly, we found increased internalization of CAIX at acidic conditions. These findings provide first evidence that intracellular drug delivery at pathophysiological conditions of malignant tumors can be attenuated by tumor antigen glycosaminoglycan modification, which is of conceptual importance in the future development of targeted cancer treatments.

  • 11.
    Conlan, Brendon
    et al.
    Australian National University, Canberra, Australia.
    Cox, Nicholas
    Australian National University, Canberra, Australia.
    Su, Ji-Hu
    Max Planck Institute for Bioinorganic Chemistry, Mülheim an der Ruhr, Germany.
    Hillier, Warwick
    Australian National University, Canberra, Australia.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lubitz, Wolfgang
    Max Planck Institute for Bioinorganic Chemistry, Mülheim an der Ruhr, Germany.
    Dutton, P Leslie
    University of Pennsylvania, Philadelphia, USA.
    Wydrzynski, Tom
    Australian National University, Canberra, Australia.
    Photo-catalytic oxidation of a di-nuclear manganese centre in an engineered bacterioferritin 'reaction centre'2009In: Biochimica et Biophysica Acta, ISSN 0006-3002, E-ISSN 1878-2434, Vol. 1787, no 9, p. 1112-1121Article in journal (Refereed)
    Abstract [en]

    Photosynthesis involves the conversion of light into chemical energy through a series of electron transfer reactions within membrane-bound pigment/protein complexes. The Photosystem II (PSII) complex in plants, algae and cyanobacteria catalyse the oxidation of water to molecular O(2). The complexity of PSII has thus far limited attempts to chemically replicate its function. Here we introduce a reverse engineering approach to build a simple, light-driven photo-catalyst based on the organization and function of the donor side of the PSII reaction centre. We have used bacterioferritin (BFR) (cytochrome b1) from Escherichia coli as the protein scaffold since it has several, inherently useful design features for engineering light-driven electron transport. Among these are: (i.) a di-iron binding site; (ii.) a potentially redox-active tyrosine residue; and (iii.) the ability to dimerise and form an inter-protein heme binding pocket within electron tunnelling distance of the di-iron binding site. Upon replacing the heme with the photoactive zinc-chlorin e(6) (ZnCe(6)) molecule and the di-iron binding site with two manganese ions, we show that the two Mn ions bind as a weakly coupled di-nuclear Mn(2)(II,II) centre, and that ZnCe(6) binds in stoichiometric amounts of 1:2 with respect to the dimeric form of BFR. Upon illumination the bound ZnCe(6) initiates electron transfer, followed by oxidation of the di-nuclear Mn centre possibly via one of the inherent tyrosine residues in the vicinity of the Mn cluster. The light dependent loss of the Mn(II) EPR signals and the formation of low field parallel mode Mn EPR signals are attributed to the formation of Mn(III) species. The formation of the Mn(III) is concomitant with consumption of oxygen. Our model is the first artificial reaction centre developed for the photo-catalytic oxidation of a di-metal site within a protein matrix which potentially mimics WOC photo-assembly.

  • 12. Conlan, Brendon l
    et al.
    Govindjee,
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry - Ångström, Uppsala University, Uppsala, Sweden.
    Thomas John Wydrzynski (8 July 1947-16 March 2018)2019In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 140, no 3, p. 253-261Article in journal (Refereed)
    Abstract [en]

    With this Tribute, we remember and honor Thomas John (Tom) Wydrzynski. Tom was a highly innovative, independent and committed researcher, who had, early in his career, defined his life-long research goal. He was committed to understand how Photosystem II produces molecular oxygen from water, using the energy of sunlight, and to apply this knowledge towards making artificial systems. In this tribute, we summarize his research journey, which involved working on soft money' in several laboratories around the world for many years, as well as his research achievements. We also reflect upon his approach to life, science and student supervision, as we perceive it. Tom was not only a thoughtful scientist that inspired many to enter this field of research, but also a wonderful supervisor and friend, who is deeply missed (see footnote*).

  • 13. Cox, Nicholas
    et al.
    Ames, William
    Epel, Boris
    Kulik, Leonid V
    Rapatskiy, Leonid
    Neese, Frank
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wieghardt, Karl
    Lubitz, Wolfgang
    Electronic Structure of a Weakly Antiferromagnetically Coupled Mn(II)Mn(III) Model Relevant to Manganese Proteins: A Combined EPR, (55)Mn-ENDOR, and DFT Study2011In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, no 17, p. 8238-8251Article in journal (Refereed)
    Abstract [en]

    An analysis of the electronic structure of the [Mn(II)Mn(III)(μ-OH)-(μ-piv)(2)(Me(3)tacn)(2)](ClO(4))(2) (PivOH) complex is reported. It displays features that include: (i) a ground 1/2 spin state; (ii) a small exchange (J) coupling between the two Mn ions; (iii) a mono-μ-hydroxo bridge, bis-μ-carboxylato motif; and (iv) a strongly coupled, terminally bound N ligand to the Mn(III). All of these features are observed in structural models of the oxygen evolving complex (OEC). Multifrequency electron paramagnetic resonance (EPR) and electron nuclear double resonance (ENDOR) measurements were performed on this complex, and the resultant spectra simulated using the Spin Hamiltonian formalism. The strong field dependence of the (55)Mn-ENDOR constrains the (55)Mn hyperfine tensors such that a unique solution for the electronic structure can be deduced. Large hyperfine anisotropy is required to reproduce the EPR/ENDOR spectra for both the Mn(II) and Mn(III) ions. The large effective hyperfine tensor anisotropy of the Mn(II), a d(5) ion which usually exhibits small anisotropy, is interpreted within a formalism in which the fine structure tensor of the Mn(III) ion strongly perturbs the zero-field energy levels of the Mn(II)Mn(III) complex. An estimate of the fine structure parameter (d) for the Mn(III) of -4 cm(-1) was made, by assuming the intrinsic anisotropy of the Mn(II) ion is small. The magnitude of the fine structure and intrinsic (onsite) hyperfine tensor of the Mn(III) is consistent with the known coordination environment of the Mn(III) ion as seen from its crystal structure. Broken symmetry density functional theory (DFT) calculations were performed on the crystal structure geometry. DFT values for both the isotropic and the anisotropic components of the onsite (intrinsic) hyperfine tensors match those inferred from the EPR/ENDOR simulations described above, to within 5%. This study demonstrates that DFT calculations provide reliable estimates for spectroscopic observables of mixed valence Mn complexes, even in the limit where the description of a well isolated S = 1/2 ground state begins to break down.

  • 14.
    Cox, Nicholas
    et al.
    Max-Planck-Institut für Chemische Energiekonversion, Mülheim an der Ruhr, Germany.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Reflections on substrate water and dioxygen formation2013In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1827, no 8-9, p. 1020-1030Article, review/survey (Refereed)
    Abstract [en]

    This brief article aims at presenting a concise summary of all experimental findings regarding substrate water-binding to the Mn4CaO5 cluster in photosystem II. Mass spectrometric and spectroscopic results are interpreted in light of recent structural information of the water oxidizing complex (WOC) obtained by x-ray crystallography, spectroscopy and theoretical modeling. Within this framework current proposals for the mechanism of photosynthetic water-oxidation are evaluated.

  • 15. Cox, Nicholas
    et al.
    Rapatskiy, Leonid
    Su, Ji-Hu
    Pantazis, Dimitrios A
    Sugiura, Miwa
    Kulik, Leonid
    Dorlet, Pierre
    Rutherford, A William
    Neese, Frank
    Boussac, Alain
    Lubitz, Wolfgang
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Effect of Ca(2+)/Sr(2+) substitution on the electronic structure of the oxygen-evolving complex of photosystem II: a combined multifrequency EPR, (55)Mn-ENDOR, and DFT study of the S(2) State2011In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 133, no 10, p. 3635-3648Article in journal (Refereed)
    Abstract [en]

    The electronic structures of the native Mn(4)O(x)Ca cluster and the biosynthetically substituted Mn(4)O(x)Sr cluster of the oxygen evolving complex (OEC) of photosystem II (PSII) core complexes isolated from Thermosynechococcus elongatus, poised in the S(2) state, were studied by X- and Q-band CW-EPR and by pulsed Q-band (55)Mn-ENDOR spectroscopy. Both wild type and tyrosine D less mutants grown photoautotrophically in either CaCl(2) or SrCl(2) containing media were measured. The obtained CW-EPR spectra of the S(2) state displayed the characteristic, clearly noticeable differences in the hyperfine pattern of the multiline EPR signal [Boussac et al. J. Biol. Chem.2004, 279, 22809-22819]. In sharp contrast, the manganese ((55)Mn) ENDOR spectra of the Ca and Sr forms of the OEC were remarkably similar. Multifrequency simulations of the X- and Q-band CW-EPR and (55)Mn-pulsed ENDOR spectra using the Spin Hamiltonian formalism were performed to investigate this surprising result. It is shown that (i) all four manganese ions contribute to the (55)Mn-ENDOR spectra; (ii) only small changes are seen in the fitted isotropic hyperfine values for the Ca(2+) and Sr(2+) containing OEC, suggesting that there is no change in the overall spin distribution (electronic coupling scheme) upon Ca(2+)/Sr(2+) substitution; (iii) the changes in the CW-EPR hyperfine pattern can be explained by a small decrease in the anisotropy of at least two hyperfine tensors. It is proposed that modifications at the Ca(2+) site may modulate the fine structure tensor of the Mn(III) ion. DFT calculations support the above conclusions. Our data analysis also provides strong support for the notion that in the S(2) state the coordination of the Mn(III) ion is square-pyramidal (5-coordinate) or octahedral (6-coordinate) with tetragonal elongation. In addition, it is shown that only one of the currently published OEC models, the Siegbahn structure [Siegbahn, P. E. M. Acc. Chem. Res.2009, 42, 1871-1880, Pantazis, D. A. et al. Phys. Chem. Chem. Phys.2009, 11, 6788-6798], is consistent with all data presented here. These results provide important information for the structure of the OEC and the water-splitting mechanism. In particular, the 5-coordinate Mn(III) is a potential site for substrate 'water' (H(2)O, OH(-)) binding. Its location within the cuboidal structural unit, as opposed to the external 'dangler' position, may have important consequences for the mechanism of O-O bond formation.

  • 16. Faunce, Thomas
    et al.
    Styring, Stenbjörn
    Wasielewski, Michael R.
    Brudvig, Gary W.
    Rutherford, A. William
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lee, Adam F.
    Hill, Craig L.
    deGroot, Huub
    Fontecave, Marc
    MacFarlane, Doug R.
    Hankamer, Ben
    Nocera, Daniel G.
    Tiede, David M.
    Dau, Holger
    Hillier, Warwick
    Wang, Lianzhou
    Amal, Rose
    Artificial photosynthesis as a frontier technology for energy sustainability2013In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 6, no 4, p. 1074-1076Article in journal (Other academic)
  • 17. Fuller, Franklin D
    et al.
    Gul, Sheraz
    Chatterjee, Ruchira
    Burgie, E Sethe
    Young, Iris D
    Lebrette, Hugo
    Srinivas, Vivek
    Brewster, Aaron S
    Michels-Clark, Tara
    Clinger, Jonathan A
    Andi, Babak
    Ibrahim, Mohamed
    Pastor, Ernest
    de Lichtenberg, Casper
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hussein, Rana
    Pollock, Christopher J
    Zhang, Miao
    Stan, Claudiu A
    Kroll, Thomas
    Fransson, Thomas
    Weninger, Clemens
    Kubin, Markus
    Aller, Pierre
    Lassalle, Louise
    Brauer, Philipp
    Miller, Mitchell D
    Amin, Muhamed
    Koroidov, Sergey
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California, USA.
    Roessler, Christian G
    Allaire, Marc
    Sierra, Raymond G
    Docker, Peter T
    Glownia, James M
    Nelson, Silke
    Koglin, Jason E
    Zhu, Diling
    Chollet, Matthieu
    Song, Sanghoon
    Lemke, Henrik
    Liang, Mengning
    Sokaras, Dimosthenis
    Alonso-Mori, Roberto
    Zouni, Athina
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry–Ångström, Molecular Biomimetics, Uppsala University, Uppsala, Sweden.
    Bergmann, Uwe
    Boal, Amie K
    Bollinger Jr, J Martin
    Krebs, Carsten
    Hogbom, Martin
    Phillips Jr, George N
    Vierstra, Richard D
    Sauter, Nicholas K
    Orville, Allen M
    Kern, Jan
    Yachandra, Vittal K
    Yano, Junko
    Drop-on-demand sample delivery for studying biocatalysts in action at X-ray free-electron lasers2017In: Nature Methods, ISSN 1548-7091, E-ISSN 1548-7105, Vol. 14, p. 443-449Article in journal (Refereed)
    Abstract [en]

    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.

  • 18. Glatzel, Pieter
    et al.
    Schroeder, Henning
    Pushkar, Yulia
    Boron, Thaddeus, III
    Mukherjee, Shreya
    Christou, George
    Pecoraro, Vincent L.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yachandra, Vittal K.
    Bergmann, Uwe
    Yano, Junko
    Electronic Structural Changes of Mn in the Oxygen-Evolving Complex of Photosystem II during the Catalytic Cycle2013In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 52, no 10, p. 5642-5644Article in journal (Refereed)
    Abstract [en]

    The oxygen-evolving complex (OEC) in photosystem II (PS II) was studied in the S-0 through S-3 states using 1s2p resonant inelastic X-ray scattering spectroscopy. The spectral changes of the OEC during the S-state transitions are subtle, indicating that the electrons are strongly delocalized throughout the cluster. The result suggests that, in addition to the Mn ions, ligands are also playing an important role in the redox reactions. A series of Mn-IV coordination complexes were compared, particularly with the PS II S-3 state spectrum to understand its oxidation state. We find strong variations of the electronic structure within the series of Mn-IV model systems. The spectrum of the S-3 state best resembles those of the Mn-IV complexes (Mn3Ca2)-Ca-IV and saplnMn(2)(IV)(OH)(2). The current result emphasizes that the assignment of formal oxidation states alone is not sufficient for understanding the detailed electronic structural changes that govern the catalytic reaction in the OEC.

  • 19.
    Han, Guangye
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, USA .
    Huang, Yang
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Koua, Faisal Hammad Mekky
    Graduate School of Natural Science and Technology, Department of Biology, Faculty of Science, Okayama University, Tsushima, Japan .
    Shen, Jian-Ren
    Graduate School of Natural Science and Technology, Department of Biology, Faculty of Science, Okayama University, Tsushima, Japan.
    Westlund, Per-Olof
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Hydration of the oxygen-evolving complex of photosystem II probed in the dark-stable S1 state using proton NMR dispersion profiles2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, no 16, p. 11924-11935Article in journal (Refereed)
    Abstract [en]

    The hydration of the oxygen-evolving complex (OEC) was characterized in the dark stable S1 state of photosystem II using water R1(ω) NMR dispersion (NMRD) profiles. The R1(ω) NMRD profiles were recorded over a frequency range from 0.01 MHz to 40 MHz for both intact and Mn-depleted photosystem II core complexes from Thermosynechococcus vulcanus (T. vulcanus). The intact-minus-(Mn)-depleted difference NMRD profiles show a characteristic dispersion from approximately 0.03 MHz to 1 MHz, which is interpreted on the basis of the Solomon-Bloembergen-Morgan (SBM) and the slow motion theories as being due to a paramagnetic enhanced relaxation (PRE) of water protons. Both theories are qualitatively consistent with the ST = 1, g = 4.9 paramagnetic state previously described for the S1 state of the OEC; however, an alternative explanation involving the loss of a separate class of long-lived internal waters due to the Mn-depletion procedure can presently not be ruled out. Using a point-dipole approximation the PRE-NMRD effect can be described as being caused by 1-2 water molecules that are located about 10 Å away from the spin center of the Mn4CaO5 cluster in the OEC. The application of the SBM theory to the dispersion observed for PSII in the S1 state is questionable, because the parameters extracted do not fulfil the presupposed perturbation criterion. In contrast, the slow motion theory gives a consistent picture indicating that the water molecules are in fast chemical exchange with the bulk (τw < 1 μs). The modulation of the zero-field splitting (ZFS) interaction suggests a (restricted) reorientation/structural equilibrium of the Mn4CaO5 cluster with a characteristic time constant of τZFS = 0.6-0.9 μs.

  • 20. Hattne, Johan
    et al.
    Echols, Nathaniel
    Tran, Rosalie
    Kern, Jan
    Gildea, Richard J.
    Brewster, Aaron S.
    Alonso-Mori, Roberto
    Gloeckner, Carina
    Hellmich, Julia
    Laksmono, Hartawan
    Sierra, Raymond G.
    Lassalle-Kaiser, Benedikt
    Lampe, Alyssa
    Han, Guangye
    Gul, Sheraz
    DiFiore, Doerte
    Milathianaki, Despina
    Fry, Alan R.
    Miahnahri, Alan
    White, William E.
    Schafer, Donald W.
    Seibert, M. Marvin
    Koglin, Jason E.
    Sokaras, Dimosthenis
    Weng, Tsu-Chien
    Sellberg, Jonas
    Latimers, Matthew J.
    Glatzel, Pieter
    Zwart, Petrus H.
    Grosse-Kunstleve, Ralf W.
    Bogan, Michael J.
    Messerschmidt, Marc
    Williams, Garth J.
    Boutet, Sebastien
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Zouni, Athina
    Yano, Junko
    Bergmann, Uwe
    Yachandra, Vittal K.
    Adams, Paul D.
    Sauter, Nicholas K.
    Accurate macromolecular structures using minimal measurements from X-ray free-electron lasers2014In: Nature Methods, ISSN 1548-7091, E-ISSN 1548-7105, Vol. 11, no 5, p. 545-548Article in journal (Refereed)
    Abstract [en]

    X-ray free-electron laser (XFEL) sources enable the use of crystallography to solve three-dimensional macromolecular structures under native conditions and without radiation damage. Results to date, however, have been limited by the challenge of deriving accurate Bragg intensities from a heterogeneous population of microcrystals, while at the same time modeling the X-ray spectrum and detector geometry. Here we present a computational approach designed to extract meaningful high-resolution signals from fewer diffraction measurements.

  • 21.
    Kawde, Anurag
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. European Synchrotron Radiation Facility (ESRF), Grenoble, France.
    Annamalai, Alagappan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Amidani, Lucia
    European Synchrotron Radiation Facility (ESRF), Grenoble, France.
    Boniolo, Manuel
    Molecular Biomimetics, Department of Chemistry – Ångström Laboratory, Uppsala University, Sweden.
    Kwong, Wai Ling
    Molecular Biomimetics, Department of Chemistry – Ångström Laboratory, Uppsala University, Sweden.
    Sellstedt, Anita
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Glatzel, Pieter
    European Synchrotron Radiation Facility (ESRF), Grenoble, France.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Molecular Biomimetics, Department of Chemistry – Ångström Laboratory, Uppsala University, Sweden.
    Photo-electrochemical hydrogen production from neutral phosphate buffer and seawater using micro-structured p-Si photo-electrodes functionalized by solution-based methods2018In: Sustainable Energy and Fuels, ISSN 2398-4902, Vol. 2, no 10, p. 2215-2223Article in journal (Refereed)
    Abstract [en]

    Solar fuels such as H2 generated from sunlight and seawater using earth-abundant materials are expected to be a crucial component of a next generation renewable energy mix. We herein report a systematic analysis of the photo-electrochemical performance of TiO2 coated, microstructured p-Si photoelectrodes (p-Si/TiO2) that were functionalized with CoOx and NiOx for H2 generation. These photocathodes were synthesized from commercial p-Si wafers employing wet chemical methods. In neutral phosphate buffer and standard 1 sun illumination, the p-Si/TiO2/NiOx photoelectrode showed a photocurrent density of 1.48 mA cm2 at zero bias (0 VRHE), which was three times and 15 times better than the photocurrent densities of p-Si/TiO2/CoOx and p-Si/TiO2, respectively. No decline in activity was observed over a five hour test period, yielding a Faradaic efficiency of 96% for H2 production. Based on the electrochemical characterizations and the high energy resolution fluorescence detected X-ray absorption near edge structure (HERFD-XANES) and emission spectroscopy measurements performed at the Ti Ka1 fluorescence line, the superior performance of the p-Si/TiO2/ NiOx photoelectrode was attributed to improved charge transfer properties induced by the NiOx coating on the protective TiO2 layer, in combination with a higher catalytic activity of NiOx for H2-evolution. Moreover, we report here an excellent photo-electrochemical performance of p-Si/TiO2/NiOx photoelectrode in corrosive artificial seawater (pH 8.4) with an unprecedented photocurrent density of 10 mA cm2 at an applied potential of 0.7 VRHE, and of 20 mA cm2 at 0.9 VRHE. The applied bias photon-to-current conversion efficiency (ABPE) at 0.7 VRHE and 10 mA cm2 was found to be 5.1%

  • 22.
    Kawde, Anurag
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Annamalai, Alagappan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boniolo, Manuel
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Cavallari, Chaira
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Glatzel, Pieter
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Si L-edge X-ray Raman spectroscopy insight on Si/TiO2 interaction in photoelectrodesManuscript (preprint) (Other academic)
  • 23.
    Kawde, Anurag
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. European Synchrotron Radiation Facility (ESRF), Grenoble, France.
    Annamalai, Alagappan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sellstedt, Anita
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Glatzel, Pieter
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Molecular Biomimetics, Department of Chemistry, Ångström Laboratory, Uppsala University, Sweden.
    A microstructured p-Si photocathode outcompetes Pt as a counter electrode to hematite in photoelectrochemical water-splitting2019In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 48, no 4, p. 1166-1170Article in journal (Refereed)
    Abstract [en]

    Herein, we communicate about an Earth-abundant semiconductor photocathode (p-Si/TiO2/NiOx) as an alternative for the rare and expensive Pt as a counter electrode for overall photoelectrochemical water splitting. The proposed photoelectrochemical (PEC) water-splitting device mimics the "Z"-scheme observed in natural photosynthesis by combining two photoelectrodes in a parallelillumination mode. A nearly 60% increase in the photocurrent density (Jph) for pristine α-Fe2Oand a 77% increase in the applied bias photocurrent efficiency (ABPE) were achieved by replacing the conventionally used Pt cathode with an efficient, cost effective p-Si/TiO2/NiOx photocathode under parallel illumination. The resulting photocurrent density of 1.26 mA cm−2 at 1.23VRHE represents a new record performance for hydrothermally grown pristine α-Fe2O3 nanorod photoanodes in combination with a photocathode, which opens the prospect for further improvement by doping α-Fe2O3 or by its decoration with co-catalysts. Electrochemical impedance spectroscopy measurements suggest that this significant performance increase is due to the enhancement of the space-charge field in α-Fe2O3. 

  • 24.
    Kawde, Anurag
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Annamalai, Alagappan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sellstedt, Anita
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Glatzel, Pieter
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Valence to core X-ray spectroscopic insight on the performance enhancing TiO2 interlayer of functionalized Si photoelectrodes for bias-free solar water splittingManuscript (preprint) (Other academic)
  • 25. Kern, Jan
    et al.
    Alonso-Mori, Roberto
    Hellmich, Julia
    Tran, Rosalie
    Hattne, Johan
    Laksmono, Hartawan
    Glöckner, Carina
    Echols, Nathaniel
    Sierra, Raymond G
    Sellberg, Jonas
    Lassalle-Kaiser, Benedikt
    Gildea, Richard J
    Glatzel, Pieter
    Grosse-Kunstleve, Ralf W
    Latimer, Matthew J
    McQueen, Trevor A
    Difiore, Dörte
    Fry, Alan R
    Messerschmidt, Marc
    Miahnahri, Alan
    Schafer, Donald W
    Seibert, M Marvin
    Sokaras, Dimosthenis
    Weng, Tsu-Chien
    Zwart, Petrus H
    White, William E
    Adams, Paul D
    Bogan, Michael J
    Boutet, Sébastien
    Williams, Garth J
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sauter, Nicholas K
    Zouni, Athina
    Bergmann, Uwe
    Yano, Junko
    Yachandra, Vittal K
    Room temperature femtosecond X-ray diffraction of photosystem II microcrystals2012In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 109, no 25, p. 9721-9726Article in journal (Refereed)
    Abstract [en]

    Most of the dioxygen on earth is generated by the oxidation of water by photosystem II (PS II) using light from the sun. This light-driven, four-photon reaction is catalyzed by the Mn(4)CaO(5) cluster located at the lumenal side of PS II. Various X-ray studies have been carried out at cryogenic temperatures to understand the intermediate steps involved in the water oxidation mechanism. However, the necessity for collecting data at room temperature, especially for studying the transient steps during the O-O bond formation, requires the development of new methodologies. In this paper we report room temperature X-ray diffraction data of PS II microcrystals obtained using ultrashort (< 50 fs) 9 keV X-ray pulses from a hard X-ray free electron laser, namely the Linac Coherent Light Source. The results presented here demonstrate that the "probe before destroy" approach using an X-ray free electron laser works even for the highly-sensitive Mn(4)CaO(5) cluster in PS II at room temperature. We show that these data are comparable to those obtained in synchrotron radiation studies as seen by the similarities in the overall structure of the helices, the protein subunits and the location of the various cofactors. This work is, therefore, an important step toward future studies for resolving the structure of the Mn(4)CaO(5) cluster without any damage at room temperature, and of the reaction intermediates of PS II during O-O bond formation.

  • 26. Kern, Jan
    et al.
    Alonso-Mori, Roberto
    Tran, Rosalie
    Hattne, Johan
    Gildea, Richard J.
    Echols, Nathaniel
    Glöckner, Carina
    Hellmich, Julia
    Laksmono, Hartawan
    Sierra, Raymond G.
    Lassalle-Kaiser, Benedikt
    Koroidov, Sergey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lampe, Alyssa
    Han, Guangye
    Gul, Sheraz
    Difiore, Dörte
    Milathianaki, Despina
    Fry, Alan R.
    Miahnahri, Alan
    Schafer, Donald W.
    Messerschmidt, Marc
    Seibert, M. Marvin
    Koglin, Jason E.
    Sokaras, Dimosthenis
    Weng, Tsu-Chien
    Sellberg, Jonas
    Latimer, Matthew J.
    Grosse-Kunstleve, Ralf W.
    Zwart, Petrus H.
    White, William E.
    Glatzel, Pieter
    Adams, Paul D.
    Bogan, Michael J.
    Williams, Garth J.
    Boutet, Sébastien
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Zouni, Athina
    Sauter, Nicholas K.
    Yachandra, Vittal K.
    Bergmann, Uwe
    Yano, Junko
    Simultaneous Femtosecond X-ray Spectroscopy and Diffraction of Photosystem II at Room Temperature2013In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 340, no 6131, p. 491-495Article in journal (Refereed)
    Abstract [en]

    Intense femtosecond x-ray pulses produced at the Linac Coherent Light Source (LCLS) were used for simultaneous x-ray diffraction (XRD) and x-ray emission spectroscopy (XES) of microcrystals of Photosystem II (PS II) at room temperature. This method probes the overall protein structure and the electronic structure of the Mn4CaO5 cluster in the oxygen-evolving complex of PS II. XRD data are presented from both the dark state (S1) and the first illuminated state (S2) of PS II. Our simultaneous XRD/XES study shows that the PS II crystals are intact during our measurements at the LCLS, not only with respect to the structure of PS II, but also with regard to the electronic structure of the highly radiation-sensitive Mn4CaO5 cluster, opening new directions for future dynamics studies.

  • 27. Kern, Jan
    et al.
    Chatterjee, Ruchira
    Young, Iris D.
    Fuller, Franklin D.
    Lassalle, Louise
    Ibrahim, Mohamed
    Gul, Sheraz
    Fransson, Thomas
    Brewster, Aaron S.
    Alonso-Mori, Roberto
    Hussein, Rana
    Zhang, Miao
    Douthit, Lacey
    de Lichtenberg, Casper
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry—Ångström, Molecular Biomimetics, Uppsala University, Uppsala, Sweden.
    Cheah, Mun Hon
    Shevela, Dmitriy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wersig, Julia
    Seuffert, Ina
    Sokaras, Dimosthenis
    Pastor, Ernest
    Weninger, Clemens
    Kroll, Thomas
    Sierra, Raymond G.
    Aller, Pierre
    Butryn, Agata
    Orville, Allen M.
    Liang, Mengning
    Batyuk, Alexander
    Koglin, Jason E.
    Carbajo, Sergio
    Boutet, Sébastien
    Moriarty, Nigel W.
    Holton, James M.
    Dobbek, Holger
    Adams, Paul D.
    Bergmann, Uwe
    Sauter, Nicholas K.
    Zouni, Athina
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Yano, Junko
    Yachandra, Vittal K.
    Structures of the intermediates of Kok’s photosynthetic water oxidation clock2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 563, p. 421-425Article in journal (Refereed)
    Abstract [en]

    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 complex3–7. 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.

  • 28. Kern, Jan
    et al.
    Tran, Rosalie
    Alonso-Mori, Roberto
    Koroidov, Sergey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Echols, Nathaniel
    Hattne, Johan
    Ibrahim, Mohamed
    Gul, Sheraz
    Laksmono, Hartawan
    Sierra, Raymond G.
    Gildea, Richard J.
    Han, Guangye
    Hellmich, Julia
    Lassalle-Kaiser, Benedikt
    Chatterjee, Ruchira
    Brewster, Aaron S.
    Stan, Claudiu A.
    Gloeckner, Carina
    Lampe, Alyssa
    DiFiore, Doertee
    Milathianaki, Despina
    Fry, Alan R.
    Seibert, M. Marvin
    Koglin, Jason E.
    Gallo, Erik
    Uhlig, Jens
    Sokaras, Dimosthenis
    Weng, Tsu-Chien
    Zwart, Petrus H.
    Skinner, David E.
    Bogan, Michael J.
    Messerschmidt, Marc
    Glatzel, Pieter
    Williams, Garth J.
    Boutet, Sebastien
    Adams, Paul D.
    Zouni, Athina
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Sauter, Nicholas K.
    Bergmann, Uwe
    Yano, Junko
    Yachandra, Vittal K.
    Taking snapshots of photosynthetic water oxidation using femtosecond X-ray diffraction and spectroscopy2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 4371-Article in journal (Refereed)
    Abstract [en]

    The dioxygen we breathe is formed by light-induced oxidation of water in photosystem II. O-2 formation takes place at a catalytic manganese cluster within milliseconds after the photosystem II reaction centre is excited by three single-turnover flashes. Here we present combined X-ray emission spectra and diffraction data of 2-flash (2F) and 3-flash (3F) photosystem II samples, and of a transient 3F' state (250 mu s after the third flash), collected under functional conditions using an X-ray free electron laser. The spectra show that the initial O-O bond formation, coupled to Mn reduction, does not yet occur within 250 mu s after the third flash. Diffraction data of all states studied exhibit an anomalous scattering signal from Mn but show no significant structural changes at the present resolution of 4.5 angstrom. This study represents the initial frames in a molecular movie of the structural changes during the catalytic reaction in photosystem II.

  • 29.
    Koroidov, Sergey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Anderlund, Magnus F
    Styring, Stenbjörn
    Thapper, Anders
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    First turnover analysis of water-oxidation catalyzed by Co-oxide nanoparticles2015In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 8, no 8, p. 2492-2503Article in journal (Refereed)
    Abstract [en]

    Co-oxides are promising water oxidation catalysts for artificial photosynthesis devices. Presently, several different proposals exist for how they catalyze O-2 formation from water. Knowledge about this process at molecular detail will be required for their further improvement. Here we present time-resolved O-18-labelling isotope-ratio membrane-inlet mass spectrometry (MIMS) experiments to study the mechanism of water oxidation in Co/methylenediphosphonate (Co/M2P) oxide nanoparticles using [Ru(bpy)(3)](3+) (bpy = 2,2'-bipyridine) as chemical oxidant. We show that O-16-Co/M2P-oxide nanoparticles produce O-16(2) during their first turnover after simultaneous addition of (H2O)-O-18 and [Ru(bpy)(3)](3+), while sequential addition with a delay of 3 s yields oxygen reflecting bulk water O-18-enrichment. This result is interpreted to show that the O-O bond formation in Co/M2P-oxide nanoparticles occurs via intramolecular oxygen coupling between two terminal Co-OHn ligands that are readily exchangeable with bulk water in the resting state of the catalyst. Importantly, our data allow the determination of the number of catalytic sites within this amorphous nanoparticular material, to calculate the TOF per catalytic site and to derive the number of holes needed for the production of the first O-2 molecule per catalytic site. We propose that the mechanism of O-O bond formation during bulk catalysis in amorphous Co-oxides may differ from that taking place at the surface of crystalline materials.

  • 30.
    Koroidov, Sergey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Anderlund, Magnus F.
    Styring, Stenbjörn
    Thapper, Anders
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mechanism of water oxidation catalyzed by Co/M2P-oxides studied by isotope-ratio membrane inlet mass spectrometryManuscript (preprint) (Other academic)
    Abstract [en]

    Co-oxides are promising water oxidation catalysts for artificial photosynthesis devices. Their catalytic mechanism was studied previously both experimentally and theoretically, but there is presently no agreement whether the O-O bond formation occurs via nucleophilic attack or by direct coupling, and whether or not bridging oxygens participate as substrate during O-O bondformation. Here we present time-resolved 18O-labelling isotope-ratio membrane-inlet massspectrometry experiments employing the previously introduced Co/methylenediphosphonate (Co/M2P) system in combination with [Ru(bpy)3]3+ (bpy = 2,2’-bipyridine) as chemical oxidant. Our data demonstrate that for Co/M2P-oxide O-O bond formation occurs between two pre-bound, fast exchanging oxygen species, i.e. likely via direct coupling between two terminal water-derived oxygen ligands. Detailed modeling of the dependence of the O2-isotope ratios on the [Ru(bpy)3]3+ concentration revealed that in the Co/M2P-oxidenanoparticles almost all Co ions are catalytically active (2.35 Co per catalytic site) and that, starting from a ‘resting state‘, 3.5 electrons need to be removed from each catalytic site for thefirst O2 formation. Since it was previously demonstrated that in the resting state most Co ions are in the oxidation state Co(III), we conclude that the coupling mechanism involves at least one Co(IV)-O radical.

  • 31.
    Koroidov, Sergey
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shevela, Dmitriy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Shutova, Tatyana
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Samuelsson, Göran
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå University, Faculty of Science and Technology, Umeå Plant Science Centre (UPSC).
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Mobile hydrogen carbonate acts as proton acceptor in photosynthetic water oxidation2014In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 11, no 17, p. 6299-6304Article in journal (Refereed)
    Abstract [en]

    Cyanobacteria, algae and plants oxidize water to the O2 we breathe, and consume CO2 during the synthesis of biomass. Although these vital processes are functionally and structurally well separated in photosynthetic organisms, there is a long-debated role for CO2/HCO3 in water oxidation. Using membrane-inlet mass spectrometry we demonstrate that HCO3 acts as a mobile proton acceptor that helps to transport the protons produced inside of photosystem II by water-oxidation out into the chloroplast's lumen, resulting in a light-driven production of O2 and CO2. Depletion of HCO3 from the media leads, in the absence of added buffers, to a reversible down-regulation of O2 production by about 20%. These findings add a previously unidentified component to the regulatory network of oxygenic photosynthesis, and conclude the more than 50-y-long quest for the function of CO2/ HCO3 in photosynthetic water oxidation.

  • 32. Krewald, Vera
    et al.
    Retegan, Marius
    Cox, Nicholas
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lubitz, Wolfgang
    DeBeer, Serena
    Neese, Frank
    Pantazis, Dimitrios A.
    Metal oxidation states in biological water splitting2015In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 6, no 3, p. 1676-1695Article in journal (Refereed)
    Abstract [en]

    A central question in biological water splitting concerns the oxidation states of the manganese ions that comprise the oxygen-evolving complex of photosystem II. Understanding the nature and order of oxidation events that occur during the catalytic cycle of five Si states (i = 0-4) is of fundamental importance both for the natural system and for artificial water oxidation catalysts. Despite the widespread adoption of the so-called "high-valent scheme"-where, for example, the Mn oxidation states in the S-2 state are assigned as III, IV, IV, IV-the competing "low-valent scheme" that differs by a total of two metal unpaired electrons (i.e. III, III, III, IV in the S-2 state) is favored by several recent studies for the biological catalyst. The question of the correct oxidation state assignment is addressed here by a detailed computational comparison of the two schemes using a common structural platform and theoretical approach. Models based on crystallographic constraints were constructed for all conceivable oxidation state assignments in the four (semi) stable S states of the oxygen evolving complex, sampling various protonation levels and patterns to ensure comprehensive coverage. The models are evaluated with respect to their geometric, energetic, electronic, and spectroscopic properties against available experimental EXAFS, XFEL-XRD, EPR, ENDOR and Mn K pre-edge XANES data. New 2.5 K Mn-55 ENDOR data of the S-2 state are also reported. Our results conclusively show that the entire S state phenomenology can only be accommodated within the high-valent scheme by adopting a single motif and protonation pattern that progresses smoothly from S-0 (III, III, III, IV) to S-3 (IV, IV, IV, IV), satisfying all experimental constraints and reproducing all observables. By contrast, it was impossible to construct a consistent cycle based on the low-valent scheme for all S states. Instead, the low-valent models developed here may provide new insight into the over-reduced S states and the states involved in the assembly of the catalytically active water oxidizing cluster.

  • 33. Krieger-Liszkay, Anja
    et al.
    Spetea, Cornelia
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry – Ångström Laboratory, Uppsala University, Molecular Biomimetic, Uppsala, Sweden.
    Photosynthesis - European Congress on Photosynthesis Research2019In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 166, no 1, p. 4-6Article in journal (Other academic)
  • 34. Kubin, Markus
    et al.
    Kern, Jan
    Gul, Sheraz
    Kroll, Thomas
    Chatterjee, Ruchira
    Löchel, Heike
    Fuller, Franklin D.
    Sierra, Raymond G.
    Quevedo, Wilson
    Weniger, Christian
    Rehanek, Jens
    Firsov, Anatoly
    Laksmono, Hartawan
    Weninger, Clemens
    Alonso-Mori, Roberto
    Nordlund, Dennis L.
    Lassalle-Kaiser, Benedikt
    Glownia, James M.
    Krzywinski, Jacek
    Moeller, Stefan
    Turner, Joshua J.
    Minitti, Michael P.
    Dakovski, Georgi L.
    Koroidov, Sergey
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Stanford PULSE Institute, SLAC National Accelerator Laboratory, Menlo Park, California 94025, USA.
    Kawde, Anurag
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kanady, Jacob S.
    Tsui, Emily Y.
    Suseno, Sandy
    Han, Zhiji
    Hill, Ethan
    Taguchi, Taketo
    Borovik, Andrew S.
    Agapie, Theodor
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry, Molecular Biomimetics, Ångström Laboratory, Uppsala University, SE 75237 Uppsala, Sweden.
    Erko, Alexei
    Föhlisch, Alexander
    Bergmann, Uwe
    Mitzner, Rolf
    Yachandra, Vittal K.
    Yano, Junko
    Wernet, Philippe
    Soft x-ray absorption spectroscopy of metalloproteins and high-valent metal-complexes at room temperature using free-electron lasers2017In: Structural dynamics, ISSN 2329-7778, Vol. 4, no 5, article id 054307Article in journal (Refereed)
    Abstract [en]

    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 similar to 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 (Mn4CaO5) 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.

  • 35.
    Kwong, Wai Ling
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Kemiskt Biologiskt Centrum (KBC) ; Department of Chemistry-Ångström Laboratory Molecular Biomimetics, Uppsala University.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lee, Cheng Choo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Sandström, Robin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Kemiskt Biologiskt Centrum (KBC) ; Department of Chemistry-Ångström Laboratory Molecular Biomimetics, Uppsala University.
    Cationic Vacancy Defects in Iron Phosphide: A Promising Route toward Efficient and Stable Hydrogen Evolution by Electrochemical Water Splitting2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 22, p. 4544-4551Article in journal (Refereed)
    Abstract [en]

    Engineering the electronic properties of transition metal phosphides has shown great effectiveness in improving their intrinsic catalytic activity for the hydrogen evolution reaction (HER) in water splitting applications. Herein, we report for the first time, the creation of Fe vacancies as an approach to modulate the electronic structure of iron phosphide (FeP). The Fe vacancies were produced by chemical leaching of Mg that was introduced into FeP as "sacrificial dopant". The obtained Fe-vacancy-rich FeP nanoparticulate films, which were deposited on Ti foil, show excellent HER activity compared to pristine FeP and Mg-doped FeP, achieving a current density of 10 mAcm(-2) at overpotentials of 108 mV in 1 m KOH and 65 mV in 0.5 m H2SO4, with a near-100% Faradaic efficiency. Our theoretical and experimental analyses reveal that the improved HER activity originates from the presence of Fe vacancies, which lead to a synergistic modulation of the structural and electronic properties that result in a near-optimal hydrogen adsorption free energy and enhanced proton trapping. The success in catalytic improvement through the introduction of cationic vacancy defects has not only demonstrated the potential of Fe-vacancy-rich FeP as highly efficient, earth abundant HER catalyst, but also opens up an exciting pathway for activating other promising catalysts for electrochemical water splitting.

  • 36.
    Kwong, Wai Ling
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lee, Cheng Choo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry-Ångström Laboratory, Uppsala University, S-75120 Uppsala, Sweden.
    Scalable Two-Step Synthesis of Nickel Iron Phosphide Electrodes for Stable and Efficient Electrocatalytic Hydrogen Evolution2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 1, p. 284-292Article in journal (Refereed)
    Abstract [en]

    The development of efficient, durable, and inexpensive hydrogen evolution electrodes remains a key challenge for realizing a sustainable H-2 fuel production via electrocatalytic water splitting. Herein, nickel-iron phosphide porous films with precisely controlled metal content were synthesized on Ti foil using a simple and scalable two-step strategy of spray-pyrolysis deposition followed by low-temperature phosphidation. The nickel-iron phosphide of an optimized Ni:Fe ratio of 1:4 demonstrated excellent overall catalytic activity for hydrogen evolution reaction (HER) in 0.5 M H2SO4, achieving current densities of -10 and -30 mA cm(-2) at overpoteritials of 101 and 123 mV, respectively, with a Tafel slope of 43 mV dec(-1). Detailed analysis obtained by X-ray diffraction, electron microscopy, electrochemistry, and X-ray photoelectron spectroscopy revealed that the superior overall HER activity of nickel iron phosphide as compared to nickel phosphide and iron phosphide was a combined effect of differences in the morphology (real surface area) and the intrinsic catalytic properties (electronic structure). Together with a long-term stability and a near-100% Faradaic efficiency, the nickel-iron phosphide electrodes produced in this study provide blueprints for large-scale H-2 production.

  • 37.
    Kwong, Wai Ling
    et al.
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Lee, Cheng Choo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Transparent Nanoparticulate FeOOH Improves the Performance of a WO3 Photoanode in a Tandem Water-Splitting Device2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 20, p. 10941-10950Article in journal (Refereed)
    Abstract [en]

    Oxygen evolution catalysts (OEC) are often employed on the surface of photoactive, semiconducting photoanodes to boost their kinetics and stability during photoelectrochemical water oxidation. However, the necessity of using optically transparent OEC to avoid parasitic light absorption by the OEC under front-side illumination is often neglected. Here, we show that furnishing the surface of a WO3 photoanode with suitable loading of FeOOH as a transparent OEC improved the photocurrent density by 300% at 1 V versus RHE and the initial photocurrent-to-O-2 Faradaic efficiency from similar to 70 to similar to 100%. The data from the photo-voltammetry, electrochemical impedance, and gas evolution measurements these improvements were a combined result of reduced hole-transfer resistance for water oxidation, minimized surface recombination of charge carriers, and improved stability against photocorrosion of WO3. We demonstrate the utility of transparent FeOOH-coated W(O)3 in a solar-powered, tandem water-splitting device by combining it with a double-junction Si solar cell and a Ni-Mo hydrogen evolution catalyst. This device performed at a solar-to-hydrogen conversion efficiency of 1.8% in near-neutral K2SO4 electrolyte.

  • 38. Kwong, Wai Ling
    et al.
    Lee, Cheng Choo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Björn, Erik
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry-Ångström Laboratory, Molecular Biomimetics, Uppsala University, 75120 Uppsala, Sweden.
    High-performance iron (III) oxide electrocatalyst for water oxidation in strongly acidic media2018In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 365, p. 29-35Article in journal (Refereed)
    Abstract [en]

    Stable and efficient oxygen evolution reaction (OER) catalysts for the oxidation of water to dioxygen in highly acidic media are currently limited to expensive noble metal (Ir and Ru) oxides since presently known OER catalysts made of inexpensive earth-abundant materials generally suffer anodic corrosion at low pH. In this study, we report that a mixed-polymorph film comprising maghemite and hematite, prepared using spray pyrolysis deposition followed by low-temperature annealing, showed a sustained OER rate (>24 h) corresponding to a current density of 10 mA cm−2 at an initial overpotential of 650 mV, with a Tafel slope of only 56 mV dec−1 and near-100% Faradaic efficiency in 0.5 M H2SO4 (pH 0.3). This performance is remarkable, since iron (III) oxide films comprising only maghemite were found to exhibit a comparable intrinsic activity, but considerably lower stability for OER, while films of pure hematite were OER-inactive. These results are explained by the differences in the polymorph crystal structures, which cause different electrical conductivity and surface interactions with water molecules and protons. Our findings not only reveal the potential of iron (III) oxide as acid-stable OER catalyst, but also highlight the important yet hitherto largely unexplored effect of crystal polymorphism on electrocatalytic OER performance.

  • 39. Kwong, Wai Ling
    et al.
    Lee, Cheng Choo
    Umeå University, Faculty of Science and Technology, Department of Plant Physiology.
    Shchukarev, Andrey
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry-Ångström Laboratory, Molecular Biomimetics, Uppsala University, 75120 Uppsala, Sweden.
    Cobalt- doped hematite thin films for electrocatalytic water oxidation in highly acidic media2019In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 55, no 34, p. 5017-5020Article in journal (Refereed)
    Abstract [en]

    Earth-abundant cobalt-doped hematite thin-film electrocatalysts were explored for acidic water oxidation. The strategically doped hematite produced a stable geometric current density of 10 mA cm(-2) for up to 50 h at pH 0.3, as a result of Co-enhanced intrinsic catalytic activity and charge transport properties across the film matrix.

  • 40.
    Liang, Yongqi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Improving BiVO4 photoanodes for solar water splitting through surface passivation2014In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 16, no 24, p. 12014-12020Article in journal (Refereed)
    Abstract [en]

    BiVO4 has shown great potential as a semiconductor photoanode for solar water splitting. Significant improvements made during recent years allowed researchers to obtain a photocurrent density of up to 4.0 mA cm(-2) (AM1.5 sunlight illumination, 1.23 V-RHE bias). For further improvements of the BiVO4 photoelectrodes, a deep understanding of the processes occurring at the BiVO4-H2O interface is crucial. Employing an electrochemical loading and removal process of NiOx, we show here that carrier recombination at this interface strongly affects the photocurrents. The removal of NiOx species by electrochemical treatment in a phosphate electrolyte leads to significantly increased photocurrents for BiVO4 photoelectrodes. At a bias of 1.23 V-RHE, the Incident Photon-to-Current Efficiency (IPCE) at 450 nm reaches 43% for the passivated BiVO4 electrode under back side illumination. A model incorporating heterogeneity of NiOx centers on the BiVO4 surface (OER catalytic centers, recombination centers, and passivation centers) is proposed to explain this improved performance.

  • 41. Lohmiller, Thomas
    et al.
    Cox, Nicholas
    Su, Ji-Hu
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Lubitz, Wolfgang
    The basic properties of the electronic structure of the oxygen-evolving complex of photosystem II are not perturbed by Ca2+ removal2012In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 287, no 29, p. 24721-24733Article in journal (Refereed)
    Abstract [en]

    Ca(2+) is an integral component of the Mn(4)O(5)Ca cluster of the oxygen-evolving complex in photosystem II (PS II). Its removal leads to the loss of the water oxidizing functionality. The S(2)' state of the Ca(2+)-depleted cluster from spinach is examined by X- and Q-band EPR and (55)Mn electron nuclear double resonance (ENDOR) spectroscopy. Spectral simulations demonstrate that upon Ca(2+) removal, its electronic structure remains essentially unaltered, i.e. that of a Mn tetramer. No redistribution of the Mn valence states and only minor perturbation of the exchange interactions between the Mn ions were found. Interestingly, the S(2)' state in spinach PS II is very similar to the native S(2) state of Thermosynechococcus elongatus in terms of spin state energies and insensitivity to methanol addition. These results assign the Ca(2+) a functional as opposed to a structural role in water splitting catalysis, such as i) being essential for efficient proton-coupled electron transfer between Y(Z) and the Mn cluster and/or ii) providing an initial binding site for substrate water. Additionally, a novel (55)Mn(2+) signal, detected by Q-band pulse EPR and ENDOR, was observed in Ca(2+)-depleted PS II. Mn(2+) titration, monitored by (55)Mn ENDOR, revealed a specific Mn(2+) binding site with a submicromolar K(D). Ca(2+) titration of Mn(2+)-loaded, Ca(2+)-depleted PS II demonstrated that the site is reversibly made accessible to Mn(2+) by Ca(2+) depletion and reconstitution. Mn(2+) is proposed to bind at one of the extrinsic subunits. This process is likely relevant for the formation of the Mn(4)O(5)Ca cluster during photoassembly and/or D1 repair.

  • 42. Lubitz, W.
    et al.
    Cox, N.
    Rapatskiy, L.
    Lohmiller, T.
    Navarro, M. Perez
    Ames, W.
    Pantazis, D.
    Neese, F.
    Boussac, N.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Light-induced water oxidation in photosynthesis2014In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 19, p. S350-S350Article in journal (Other academic)
  • 43. Lubitz, Wolfgang
    et al.
    Reijerse, Edward J
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Chemistry.
    Solar water-splitting into H2 and O2: design principles of photosystem II and hydrogenases2008In: Energy & Environmental Science, Vol. 1, no 1, p. 15-31Article in journal (Refereed)
    Abstract [en]

    This review aims at presenting the principles of water-oxidation in photosystem II and of hydrogen production by the two major classes of hydrogenases in order to facilitate application for the design of artificial catalysts for solar fuel production.

  • 44. Melder, Jens
    et al.
    Kwong, Wai Ling
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Molecular Biomimetics, Department of Chemistry, Ångström Laboratory, Uppsala Universitet.
    Shevela, Dmitriy
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Molecular Biomimetics, Department of Chemistry, Ångström Laboratory, Uppsala Universitet.
    Kurz, Philipp
    Electrocatalytic Water Oxidation by MnOx/C: In Situ Catalyst Formation, Carbon Substrate Variations, and Direct O2/CO2 Monitoring by Membrane-Inlet Mass Spectrometry2017In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 22, p. 4491-4502Article in journal (Refereed)
    Abstract [en]

    Layers of amorphous manganese oxides were directly formed on the surfaces of different carbon materials by exposing the carbon to aqueous solutions of permanganate (MnO4- ) followed by sintering at 100-400 °C. During electrochemical measurements in neutral aqueous buffer, nearly all of the MnOx /C electrodes show significant oxidation currents at potentials relevant for the oxygen evolution reaction (OER). However, by combining electrolysis with product detection by using mass spectrometry, it was found that these currents were only strictly linked to water oxidation if MnOx was deposited on graphitic carbon materials (faradaic O2 yields >90 %). On the contrary, supports containing sp3 -C were found to be unsuitable as the OER is accompanied by carbon corrosion to CO2 . Thus, choosing the "right" carbon material is crucial for the preparation of stable and efficient MnOx /C anodes for water oxidation catalysis. For MnOx on graphitic substrates, current densities of >1 mA cm-2 at η=540 mV could be maintained for at least 16 h of continuous operation at pH 7 (very good values for electrodes containing only abundant elements such as C, O, and Mn) and post-operando measurements proved the integrity of both the catalyst coating and the underlying carbon at OER conditions.

  • 45.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    An Institutional Approach to Solar Fuels Research2012In: Australian journal of chemistry (Print), ISSN 0004-9425, E-ISSN 1445-0038, Vol. 65, no 6, p. 573-576Article in journal (Refereed)
    Abstract [en]

    This account gives a brief overview of various directions in current solar fuels research. On that basis, the necessity for an interdisciplinary approach is argued, and an institutional way for promoting this development is presented using the example of the Chemistry Biology Centre (KBC) at Umeå University in Sweden.

  • 46.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Biophysical perceptions of the structure and mechanism of the water-oxidizing complex in photosystem II:  2011In:  :  , 2011Conference paper (Other academic)
  • 47.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Catalysts for solar water splitting2009In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 2, no 1, p. 47-48Article in journal (Refereed)
    Abstract [en]

    Making H2 while the sun shines: Recently, an inorganic catalyst based on Co2+ and phosphate ions was developed that operates in neutral water under ambient conditions to produce O2 from H2O at low overpotentials. Coupling the setup to a counter electrode at which H2 formation takes place as well as to a solar cell could lead to solar water splitting into H2 and O2.

  • 48.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Water Oxidation in Photosystem II: Structure and Function of Nature’s Mn4CaO5 Cluster2011Conference paper (Other academic)
    Abstract [en]

    Photosynthesis is Nature‟s way of utilizing solar energy. Photosystem II (PSII) is the unique pigment-protein complex of photosynthesis that is able to perform visible light-driven oxidation of water into O2, protons and energized electrons. The catalytic site of water-oxidation in PSII is referred to as the water-oxidizing complex (WOC) and contains a Mn4CaO5 cluster that accumulates in a cyclic reaction four oxidizing equivalents before water-oxidation occurs. Since it is possible to combine protons and electrons in a subsequent step to H2, PSII is frequently viewed as blueprint for developing man-made catalysts for storing solar energy in the chemical bonds of H2 and O2.1 This talk will report on recent dramatic improvements regarding the understanding of the geometric and electronic structures of the WOC and especially of its Mn4CaO5 cluster. These improvements are based on X-ray crystallographic data by Zouni et al.2 and Shen and coworkers3, but crucial information also comes from EXAFS4-11 and EPR/ENDOR studies12-16 and from theoretical calculations17-20. Furthermore the energetic of the O2 release step21 will be discussed and the mode of substrate water binding22. Possible mechanism for photosynthetic water-oxidation23-25 and activity measurements of synthetic Mn4CaO5 complexes will be briefly covered26-28.

  • 49.
    Messinger, Johannes
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Alia, A
    Leiden Institute of Chemistry, Leiden University, Leiden, The Netherlands.
    Govindjee,
    Department of Plant Biology, Department of Biochemistry, Center of Biophysics and Computational Biology, University of Illinois, Urbana, USA.
    Special educational issue on ‘Basics and application of biophysical techniques in photosynthesis and related processes’2009In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 101, no 2-3, p. 89-92Article in journal (Refereed)
  • 50.
    Messinger, Johannes
    et al.
    Umeå University, Faculty of Science and Technology, Chemistry.
    Alia, A
    Govindjee,
    Special educational issue on 'Basics and application of biophysical techniques in photosynthesis and related processes'-Part B2009In: Photosynthesis research, ISSN 1573-5079, Vol. 102, no 2-3, p. 103-6Article in journal (Refereed)
    Abstract [en]

    Without Abstract This is a slightly revised re-publication of the guest editorial in Photosynthesis Research, vol. 101, issue nos. 2–3, 2009.

12 1 - 50 of 87
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