uu.seUppsala University Publications
Change search
Refine search result
1 - 46 of 46
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Anderlund, Magnus F.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Högblom, Joakim
    Shi, Wei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Eriksson, Lars
    Weihe, Högni
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Åkermark, Björn
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Redox chemistry of a dimanganese(II,III) complex with an unsymmetric ligand: Water binding, deprotonation and accumulative light-induced oxidation2006In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 24, p. 5033-5047Article in journal (Refereed)
    Abstract [en]

    A dinuclear manganese complex {[(Mn2L)-L-II,IIII(mu-OAc)(2)]-ClO4} has been synthesised, where L is the dianion of 2-{[bis-(pyrid-2-ylmethyl)amino]methyl}-6-{[(3,5-di-tert-butyl-2- hydroxybenzyl)(pyrid-2-ylmethyl)amino]methyl)-4-methylphenol, an unsymmetric binucleating ligand with two coordinating phenol groups. The two manganese ions, with a Mn-Mn distance of 3.498 angstrom, are bridged by the two bidentate acetate ligands and the 4-methylphenolate group of the ligand, resulting in a N3O3 and N2O4 donor set of Mn-II and Mn-II, respectively. Electrochemically [Mn2(II,III)L(mu-OAc)(2)](+) is reduced to [(Mn2L)-L-II,II(mu-OAc)(2)] at E-1/2(1)=-0.53 V versus Fc(+/0) and oxidised to [(Mn2L)-L-III,III(mu-OAC)(2)](2+) at E-1/2(2)=0.38 V versus Fc(+/0). All three redox states have been characterised by EPR, IR and UV/Vis spectroscopy. Subsequent oxidation of [(Mn2L)-L-II,III(mu-OAc)(2)](2+) [E-1/2(3)=0.75 V vs. Fc(+/0)] in dry acetonitrile results in an unstable primary product with a lifetime of about 100 ins. At high scan rates quasireversible voltammetric behaviour is found for all three electrode processes, with particularly slow electron transfer for the II,III/II,II [k(o)(1) = 0.002 cms(-1) and III,III/II,III [k(o)(2) = 0.005 cms(-1)] couples, which can be rationalised in terms of major distortions of the Mn-II centres. In aqueous media the bridging acetates are replaced by water-derived ligands. Deprotonation of these stabilises higher valence states, and photo-induced oxidation of the manganese complex results in a (Mn2L)-L-IlI,IV complex with oxo or hydroxo bridging ligands, which is further oxidised to an EPR-silent product. These results demonstrate that a larger number of metal-centred oxidations can be compressed in a narrow potential range if build up of charge is avoided by charge-compensating reactions.

  • 2. Berggren, Gustav
    et al.
    Anderlund, Magnus, F.
    Magnuson, Ann
    Åkermark, Björn
    Eriksson, Lars
    Sodium [1,2-bis(2-methyl-2-oxopropanamido)-benzene](tetrahydrofuran) manganese(III) methanol solvate2005In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, ISSN 1600-5368, Vol. 61, p. M1169-M1171Article in journal (Refereed)
  • 3. Borgström, Magnus
    et al.
    Shaikh, Nizamuddin
    Johansson, Olof
    Anderlund, Magnus F
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Åkermark, Björn
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Light-Induced Manganese Oxidation and Long-Lived Charge Separation in a Mn2II,II─RuII─Acceptor Triad.2005In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, p. 17504-17515Article in journal (Refereed)
  • 4.
    Cardona, Tanai
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Battchikova, Natalia
    Agervald, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Zhang, Pengpeng
    Nagel, Erik
    Aro, Eva-Mari
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Isolation and characterization of thylakoid membranes from the filamentous cyanobacterium Nostoc punctiforme2007In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 131, no 4, p. 622-634Article in journal (Refereed)
    Abstract [en]

    Nostoc punctiforme strain Pasteur Culture Collection (PCC) 73102, a sequenced filamentous cyanobacterium capable of nitrogen fixation, is used as a model organism for characterization of bioenergetic processes during nitrogen fixation in Nostoc. A protocol for isolating thylakoid membranes was developed to examine the biochem. and biophys. aspects of photosynthetic electron transfer. Thylakoids were isolated from filaments of N. punctiforme by pneumatic pressure-drop lysis. The activity of photosynthetic enzymes in the isolated thylakoids was analyzed by measuring oxygen evolution activity, fluorescence spectroscopy and ESR spectroscopy. Electron transfer was found functional in both PSII and PSI. Electron transfer measurements in PSII, using diphenylcarbazide as electron donor and 2,6-dichlorophenolindophenol as electron acceptor, showed that 80% of the PSII centers were active in water oxidn. in the final membrane prepn. Anal. of the membrane protein complexes was made by 2D gel electrophoresis, and identification of representative proteins was made by mass spectrometry. The ATP synthase, several oligomers of PSI, PSII and the NAD(P)H dehydrogenase (NDH)-1L and NDH-1M complexes, were all found in the gels. Some differences were noted compared with previous results from Synechocystis sp. PCC 6803. Two oligomers of PSII were found, monomeric and dimeric forms, but no CP43-less complexes. Both dimeric and monomeric forms of Cyt b6/f could be obsd. In all, 28 different proteins were identified, of which 25 are transmembrane proteins or membrane associated ones.

  • 5.
    Cardona, Tanai
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Battchikova, Natalia
    Department of Biology, University of Turku.
    Zhang, Pengpeng
    Department of Biology, University of Turku.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Aro, Eva-Mari
    Department of Biology, University of Turku.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Electron transfer protein complexes in the thylakoid membranes of heterocysts from the cyanobacterium Nostoc punctiforme2009In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1787, no 4, p. 252-263Article in journal (Refereed)
    Abstract [en]

    Filamentous, heterocystous cyanobacteria are capable of nitrogen fixation and photoautotrophic growth. Nitrogen fixation takes place in heterocysts that differentiate as a result of nitrogen starvation. Heterocysts uphold a microoxic environment to avoid inactivation of nitrogenase, e.g. by downregulation of oxygenic photosynthesis. The ATP and reductant requirement for the nitrogenase reaction is considered to depend on Photosystem I, but little is known about the organization of energy converting membrane proteins in heterocysts. We have investigated the membrane proteome of heterocysts from nitrogen fixing filaments of Nostoc punctiforme sp. PCC 73102, by 2D gel electrophoresis and mass spectrometry. The membrane proteome was found to be dominated by the Photosystem I and ATP-synthase complexes.We could identify asignificant amount of assembled Photosystem II complexes containing the D1, D2, CP43, CP47 and PsbO proteins from these complexes. We could also measure light-driven in vitro electron transfer from Photosystem II in heterocyst thylakoid membranes. We did not find any partially disassembled PhotosystemII complexes lacking the CP43 protein. Several subunits of the NDH-1 complex were also identified. The relative amount of NDH-1M complexes was found to be higher than NDH-1L complexes, which might suggest a role for this complex in cyclic electron transfer in the heterocysts of Nostoc punctiforme.

  • 6.
    Cardona, Tanai
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Excitation energy transfer to Photosystem I in filaments and heterocysts of Nostoc punctiforme2010In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1797, no 3, p. 425-433Article in journal (Refereed)
    Abstract [en]

    Cyanobacteria adapt to varying light conditions by controlling the amount of excitation energy to the photosystems. On the minute time scale this leads to redirection of the excitation energy, usually referred to as state transitions, which involves movement of the phycobilisomes. We have studied short-term light adaptation in isolated heterocysts and intact filaments from the cyanobacterium Nostoc punctiforme ATCC 29133. In N. punctiforme vegetative cells differentiate into heterocysts where nitrogen fixation takes place. Photosystem II is inactivated in the heterocysts, and the abundancy of Photosystem I is increased relative to the vegetative cells. To study light-induced changes in energy transfer to Photosystem I, pre-illumination was made to dark adapted isolated heterocysts. Illumination wavelengths were chosen to excite Photosystem I (708 nm) or phycobilisomes (560. nm) specifically. In heterocysts that were pre-illuminated at 708. nm, fluorescence from the phycobilisome terminal emitter was observed in the 77 K emission spectrum. However, illumination with 560. nm light caused quenching of the emission from the terminal emitter, with a simultaneous increase in the emission at 750 nm, indicating that the 560 nm pre-illumination caused trimerization of Photosystem I. Excitation spectra showed that 560 nm pre-illumination led to an increase in excitation transfer from the phycobilisomes to trimeric Photosystem I. Illumination at 708 nm did not lead to increased energy transfer from the phycobilisome to Photosystem I compared to dark adapted samples. The measurements were repeated using intact filaments containing vegetative cells, and found to give very similar results as the heterocysts. This demonstrates that molecular events leading to increased excitation energy transfer to Photosystem I, including trimerization, are independent of Photosystem II activity.

  • 7. Fryxelius, Jacob
    et al.
    Eilers, Gerriet
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry.
    Feyziyev, Yashar
    Magnuson, Ann
    Sun, Licheng
    Lomoth, Reiner
    Synthesis and redox properties of a [meso-tris(4-nitrophenyl) corrolato]Mn(III) complex.2005In: Journal of Porphyrins and Phthalocyanines, ISSN 1088-4246, E-ISSN 1099-1409, no 9(6), p. 379-386Article in journal (Refereed)
  • 8.
    Hammarström, Leif
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science. Physics, Department of Physics and Materials Science, Chemical Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Johansson, Olof
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science. Physics, Department of Physics and Materials Science, Chemical Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science. Physics, Department of Physics and Materials Science, Chemical Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Artificial Photosynthesis Edited by Anthony F. Collings and Christa Critchley2006In: Angewandte Chemie, International Edition, 2006Chapter in book (Other (popular scientific, debate etc.))
  • 9.
    Huang, Ping
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Högblom, Joakim
    Anderlund, Magnus F
    Sun, Licheng
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Light-Induced Multistep Oxidation of Dinuclear Manganese Complexes for Artificial Photosynthesis.2004In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 98, no 5, p. 733-745Article in journal (Refereed)
  • 10.
    Huang, Ping
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Abrahamsson, Malin
    Tamm, Markus
    Sun, Licheng
    van Rotterdam, Bart
    Park, Jonathan
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Åkermark, Björn
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Photo-induced oxidation of a dinuclear Mn-2(II,II) complex to the Mn-2(III,IV) state by inter- and intramolecular electron transfer to Ru-III tris-bipyridine2002In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 91, no 1, p. 159-172Article in journal (Refereed)
    Abstract [en]

    To model the structural and functional parts of the water oxidizing complex in Photosystem 11, a dimeric manganese(II,11) complex (1) was linked to a ruthenium(II)tris-bipyridine (Ru-II(bpy)3) complex via a substituted L-tyrosine, to form the trinuclear complex 2 [J. Inorg. Biochem. 78 (2000) 15]. Flash photolysis of 1 and Ru-II(bpy), in aqueous solution, in the presence of an electron acceptor, resulted in the stepwise extraction of three electrons by Ru-III(bpy), from the Mn-2(II,II) dimer, which then attained the Mn-2(III,IV) oxidation state. In a similar experiment with compound 2, the dinuclear Mn complex reduced the photo-oxidized Ru moiety via intramolecular electron transfer on each photochemical event. From EPR it was seen that 2 also reached the Mn-2(III,IV) state. Our data indicate that oxidation from the Mn-2(II,II) state proceeds stepwise via intermediate formation of Mn-2(II,III) and Mn-2(III,III). In the presence of water, cyclic voltammetry showed an additional anodic peak beyond Mn-2(II,III/III,III) oxidation which was significantly lower than in neat acetonitrile. Assuming that this peak is due to oxidation to Mn-2(III,IV), this suggests that water is essential for the formation of the Mn-2(III,IV) oxidation state. Compound 2 is a structural mimic of the water oxidizing complex, in that it links a Mn complex via a tyrosine to a highly oxidizing photosensitizer. Complex 2 also mimics mechanistic aspects of Photosystem 11, in that the electron transfer to the photosensitizer is fast and results in several electron extractions from the Mn moiety. (C) 2002 Elsevier Science Inc. All rights reserved.

  • 11. Johansson, Anh
    et al.
    Abrahamsson, Malin
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mårtensson, J
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Åkermark, Björn
    Synthesis and Photophysics of One Mononuclear Mn(III) and One Dinuclear Mn(III,III) Complex Covalently Linked to a Ruthenium(II) tris-Bipyridyl Complex.2003In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 42, no 23, p. 7502-7511Article in journal (Refereed)
  • 12.
    Johansson, Anh
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Abrahamsson, Malin
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mårtensson, Jerker
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Åkermark, Björn
    Synthesis and Photophysics of One Mononuclear Mn(III) and One Dinuclear Mn(III,III) Complex Covalently Linked to a Ruthenium(II) Tris(bipyridyl) Complex2003In: Inorganic Chemistry, Vol. 42, p. 7502-7511Article in journal (Refereed)
    Abstract [en]

    The preparation of donor (D)-photosensitizer (S) arrays, consisting of a manganese complex as D and a ruthenium tris(bipyridyl) complex as S has been pursued. Two new ruthenium complexes containing coordinating sites for one (2a) and two manganese ions (3a) were prepared in order to provide models for the donor side of photosystem II in green plants. The manganese coordinating site consists of bridging and terminal phenolate as well as terminal pyridyl ligands. The corresponding ruthenium-manganese complexes, a manganese monomer 2b and dimer 3b, were obtained. For the dimer 3b, our data suggest that intramolecular electron transfer from manganese to photogenerated ruthenium(III) is fast, k(ET) > 5 x 10(7) s(-1).

  • 13.
    Li, Xin
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mustila, Henna
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Homologous overexpression of NpDps2 and NpDps5 increases the tolerance for oxidative stress in the multicellular cyanobacterium Nostoc punctiforme2018In: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 365, no 18, article id fny198Article in journal (Refereed)
    Abstract [en]

    The filamentous cyanobacterium Nostoc punctiforme has several oxidative stress-managing systems, including Dps proteins. Dps proteins belong to the ferritin superfamily and are involved in abiotic stress management in prokaryotes. Previously, we found that one of the five Dps proteins in N. punctiforme, NpDps2, was critical for H2O2 tolerance. Stress induced by high light intensities is aggravated in N. punctiforme strains deficient of either NpDps2, or the bacterioferritin-like NpDps5. Here, we have investigated the capacity of NpDps2 and NpDps5 to enhance stress tolerance by homologous overexpression of these two proteins in N. punctiforme. Both overexpression strains were found to tolerate twice as high concentrations of added H2O2 as the control strain, indicating that overexpression of either NpDps2 or NpDps5 will enhance the capacity for H2O2 tolerance. Under high light intensities, the overexpression of the two NpDps did not enhance the tolerance against general light-induced stress. However, overexpression of the heterocyst-specific NpDps5 in all cells of the filament led to a higher amount of chlorophyll-binding proteins per cell during diazotrophic growth. The OENpDps5 strain also showed an increased tolerance to ammonium-induced oxidative stress. Our results provide information of how Dps proteins may be utilised for engineering of cyanobacteria with enhanced stress tolerance.

  • 14.
    Lomoth, Reiner
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Sjödin, Martin
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Mimicking the electron donor side of Photosystem II in artificial photosynthesis.2006In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, p. 1-16Article in journal (Refereed)
  • 15.
    Lomoth, Reiner
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Magnuson, Ann
    Xu, Yunhua
    Sun, Licheng
    Mixed-Valance Properties of an Acetate-Bridged Dinuclear Ruthenium (II,II) Complex2003In: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215, Vol. 107, p. 4373-4380Article in journal (Refereed)
  • 16.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Heterocyst Thylakoid Bioenergetics2019In: LIFE-BASEL, ISSN 2075-1729, Vol. 9, no 1, article id 13Article, review/survey (Refereed)
    Abstract [en]

    Heterocysts are specialized cells that differentiate in the filaments of heterocystous cyanobacteria. Their role is to maintain a microoxic environment for the nitrogenase enzyme during diazotrophic growth. The lack of photosynthetic water oxidation in the heterocyst puts special constraints on the energetics for nitrogen fixation, and the electron transport pathways of heterocyst thylakoids are slightly different from those in vegetative cells. During recent years, there has been a growing interest in utilizing heterocysts as cell factories for the production of fuels and other chemical commodities. Optimization of these production systems requires some consideration of the bioenergetics behind nitrogen fixation. In this overview, we emphasize the role of photosynthetic electron transport in providing ATP and reductants to the nitrogenase enzyme, and provide some examples where heterocysts have been used as production facilities.

  • 17.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Anderlund, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Johansson, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Polivka, Tomas
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Sundström, Villy
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Biomimetic and Microbial Approaches to Solar Fuel Generation2009In: Accounts of Chemical Research, ISSN 0001-4842, E-ISSN 1520-4898, Vol. 42, no 12, p. 1899-1909Article, review/survey (Refereed)
    Abstract [en]

    Photosynthesis is performed by a multitude of organisms, but in P nearly all cases, it is variations on a common theme: absorption of light followed by energy transfer to a reaction center where charge separation takes place, This initial form of chemical energy is stabilized by the biosynthesis of carbohydrates. To produce these energy-rich products, a substrate is needed that feeds in reductive equivalents, When photosynthetic microorganisms learned to use water as a substrate some 2 billion years ago, a fundamental barrier against unlimited use of solar energy was overcome. The possibility of solar energy use has inspired researchers to construct artificial photosynthetic systems that show analogy to parts of the intricate molecular machinery of photosynthesis. Recent years have seen a reorientation of efforts toward creating integrated light-to-fuel systems that can use solar energy for direct synthesis of energy-rich compounds, so-called solar fuels. Sustainable production of solar fuels is a long awaited development that promises extensive solar energy use combined with long-term storage. The stoichiometry of water splitting into molecular oxygen, protons, and electrons is deceptively simple; achieving it by chemical catalysis has proven remarkably difficult. The reaction center Photosystem II couples light-induced charge separation to an efficient molecular water-splitting catalyst, a Mn4Ca complex, and is thus an important template for biomimetic chemistry. In our aims to design biomimetic manganese complexes for light-driven water oxidation, we link photosensitizers and charge-separation motifs to potential catalysts in supramolecular assemblies. In photosynthesis, production of carbohydrates demands the delivery of multiple reducing equivalents to CO2. In contrast, the two-electron reduction of protons to molecular hydrogen is much less demanding. Virtually all microorganisms have enzymes called hydrogenases that convert protons to hydrogen, many of them with good catalytic efficiency. The catalytic sites of hydrogenases are now the center of attention of biomimetic efforts, providing prospects for catalytic hydrogen production with inexpensive metals. Thus, we might complete the water-to-fuel conversion: light + 2H(2)O -> 2H(2) + O-2 This reaction formula is to some extent already elegantly fulfilled by cyanobacteria and green algae, water-splitting photosynthetic microorganisms that under certain conditions also can produce hydrogen. An alternative route to hydrogen from solar energy is therefore to engineer these organisms to produce hydrogen more efficiently. This Account describes our original approach to combine research in these two fields: mimicking structural and functional principles of both Photosystem II and hydrogenases by synthetic chemistry and engineering cyanobacteria to become better hydrogen producers and ultimately developing new routes toward synthetic biology.

  • 18. Magnuson, Ann
    et al.
    Berglund, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Korall, Peter
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Akermark, Björn
    Styring, Stenbjörn
    Sun, Licheng
    Mimicking electron transfer reactions in photosystem II: synthesis and photochemical characterization of a ruthenium(II) tris(bipyridyl) complex with a covalently linked tyrosine.1997In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 119, no 44, p. 10720-10725Article in journal (Refereed)
    Abstract [en]

    In the natural photosynthetic reaction center photosystem II, absorption of a photon leads to photooxidationof the primary electron donor P680, which subsequently retrieves electrons from a tyrosyl residue, functioning as aninterface to the oxygen-evolving manganese complex. In a first step toward mimicking these reactions, we havemade a Ru(II)-polypyridine complex with an attached tyrosyl moiety. The photoexcited ruthenium complex playedthe role of P680and was first oxidized by external acceptors. Combined transient absorbance and EPR studies provided evidence that the Ru(III) formed was reduced by intramolecular electron transfer from the attached tyrosine, with a rate constant of 5104s-1. Thus we show that a tyrosine radical could be formed by light-induced electrontransfer reactions, and we indicate future directions for developing a closer analogy with the photosystem II reactions.

  • 19. Magnuson, Ann
    et al.
    Berglund, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Korall, Peter
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry I.
    Åkermark, Björn
    Styring, Stenbjörn
    Sun, Licheng
    Mimicing Electron Transfer Reactions in Photosystem II: Synthesis and Photochemical Characterization of a Ruthenium(II) Tris(bipyridyl) Complex with a Covalently Linked Tyrosine1997In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 119, no 44, p. 10720-10725Article in journal (Refereed)
  • 20.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Cardona, Tanai
    Imperial College London.
    Thylakoid membrane function in heterocysts2016In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1857, no 3, p. 309-319Article, review/survey (Refereed)
    Abstract [en]

    Multicellular cyanobacteria form different cell types in response to environmental stimuli. Under nitrogen limiting conditions a fraction of the vegetative cells in the filament differentiate into heterocysts. Heterocysts are specialized in atmospheric nitrogen fixation and differentiation involves drastic morphological changes on the cellular level, such as reorganization of the thylakoid membranes and differential expression of thylakoid membrane proteins. Heterocysts uphold a microoxic environment to avoid inactivation of nitrogenase by developing an extra polysaccharide layer that limits air diffusion into the heterocyst and by upregulating heterocyst-specific respiratory enzymes. In this review article, we summarize what is known about the thylakoid membrane in heterocysts and compare its function with that of the vegetative cells. We emphasize the role of photosynthetic electron transport in providing the required amounts of ATP and reductants to the nitrogenase enzyme. In the light of recent high-throughput proteomic and transcriptomic data, as well as recently discovered electron transfer pathways in cyanobacteria, our aim is to broaden current views of the bioenergetics of heterocysts. This article is part of a Special Issue entitled: Bioenergetic systems in bacteria.

  • 21.
    Magnuson, Ann
    et al.
    Department of Biochemistry, Center for Chemistry and Chemical Engineering, Lund University.
    Frapart, Yves
    Abrahamsson, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Horner, Olivier
    Åkermark, Björn
    Sun, Licheng
    Girerd, Jean-Jaques
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    A Biomimetic Model System for the Water Oxidizing Triad in Photosystem II1999In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 121, no 1, p. 89-96Article in journal (Refereed)
    Abstract [en]

    In plants, solar energy is used to extract electrons from water, producing atmospheric oxygen. This is conducted by Photosystem II, where a redox ”triad” consisting of chlorophyll, a tyrosine, and a manganese cluster, governs an essential part of the process. Photooxidation of the chlorophylls produces electron transfer from the tyrosine, which forms a radical. The radical and the manganese cluster together extract electrons from water, providing the biosphere with an unlimited electron source. As a partial model for this system we constructed a ruthenium(II) complex with a covalently attached tyrosine, where the photooxidized ruthenium was rereduced by the tyrosine. In this study we show that the tyrosyl radical, which gives a transient EPR signal under illumination, can oxidize a manganese complex. The dinuclear manganese complex, which initially is in the Mn(III)/(III) state, is oxidized by the photogenerated tyrosyl radical to the Mn(III)/(IV) state. The redox potentials in our system are comparable to those in Photosystem II. Thus, our synthetic redox “triad” mimics important elements in the electron donor ”triad” in Photosystem II, significantly advancing the development of systems for artificial photosynthesis based on ruthenium−manganese complexes.

  • 22.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Krassen, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Ho, Felix M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Modeling Photosystem I with the alternative reaction center protein PsaB2 in the nitrogen fixing cyanobacterium Nostoc punctiforme2011In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1807, no 9, p. 1152-1161Article in journal (Refereed)
    Abstract [en]

    Five nitrogen fixing cyanobacterial strains have been found to contain PsaB2, an additional and divergent gene copy for the Photosystem I reaction center protein PsaB. In all five species the divergent gene, psaB2, is located separately from the normal psaAB operon in the genome. The protein, PsaB2, was recently identified in heterocysts of Nostoc punctiforme sp. strain PCC 73102. 12 conserved amino acid replacements and one insertion, were identified by a multiple sequence alignment of several PsaB2 and PsaB1 sequences. Several, including an inserted glutamine, are located close to the iron-sulfur cluster F(x) in the electron transfer chain. By homology modeling, using the Photosystem I crystal structure as template, we have found that the amino acid composition in PsaB2 will introduce changes in critical parts of the Photosystem I protein structure. The changes are close to F(x) and the phylloquinone (PhQ) in the B-branch, indicating that the electron transfer properties most likely will be affected. We suggest that the divergent PsaB2 protein produces an alternative Photosystem I reaction center with different structural and electron transfer properties. Some interesting physiologcial consequences that this can have for the function of Photosystem I in heterocysts, are discussed.

  • 23.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Liebisch, Peter
    Haumann, Michael
    Högblom, Joakim
    Anderlund, Magnus F
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Meyer-Klaucke, Wolfram
    Dau, Holger
    Bridging-mode changes facilitate successive oxidation steps at about 1 V in two binuclear manganese complexes - implications for photosynthetic water-oxidation.2006In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 100, p. 1234-1243Article in journal (Refereed)
  • 24.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Raleiras, Patricia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Laser flash photolysis induced electron transfer in the isolated uptake hydrogenase subunit HupS studied by EPR spectroscopy2014In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 19, no S2, p. 851-Article in journal (Other academic)
  • 25.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Raleiras, Patricia
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Meszaros, Livia S.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Khanna, Namita
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Miranda, Helder
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ho, Felix M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Sustainable photobiological hydrogen production via protein engineering of cyanobacterial hydrogenases2018In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 255Article in journal (Other academic)
  • 26. Magnuson, Ann
    et al.
    Rova, Maria
    Mamedov, Fikret
    Fredriksson, Per-Olaf
    Styring, Stenbjörn
    The role of cytochrome b559 and tyrozineD in protection against photoinhibition during in vivo photoactivation of photosystem II1999In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1411, p. 180-191Article in journal (Refereed)
  • 27.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Rova, Maria
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Fredriksson, P.-O.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Changes in the oxidation state of cytochrome b559 and tyrosine-D during in vivo photoactivation of photosystem II1998In: Photosynthesis: Mechanisms and Effects / [ed] Garab, G., Kluwer Academic Publishers, 1998, p. 1097-1100Conference paper (Refereed)
  • 28.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Molecular Chemistry for Solar Fuels: From Natural to Artificial Photosynthesis2012In: Australian journal of chemistry (Print), ISSN 0004-9425, E-ISSN 1445-0038, Vol. 65, no 6, p. 564-572Article, review/survey (Refereed)
    Abstract [en]

    The world needs new, environmentally friendly, and renewable fuels to exchange for fossil fuels. The fuel must be made from cheap, abundant, and renewable resources. The research area of solar fuels aims to meet this demand. This paper discusses why we need a solar fuel, and proposes solar energy as the major renewable energy source to feed from. The scientific field concerning artificial photosynthesis is expanding rapidly and most of the different scientific visions for solar fuels are briefly reviewed. Research strategies for the development of artificial photosynthesis to produce solar fuels are overviewed, with some critical concepts discussed in closer detail.

  • 29.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics. Avdelningen för molekylär biomimetik.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, L.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Understanding Photosystem II function by artificial photosynthesis2005In: Photosystem II: The Water/Plastoquinone Oxido-Reductase in Photosynthesis / [ed] Wydrzynski, T, Springer, Dordrecht, Netherlands , 2005, p. 753-775Chapter in book (Other academic)
  • 30.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Understanding Photosystem II Function by Artificial Photosynthesis2005In: Photosystem II: The Light-Driven Water:Plastoquinone Oxidoreductase / [ed] Wydrzynski, Thomas J.; Satoh, Kimiyuki; Freeman, Joel A., Springer Netherlands, 2005, p. 753-775Chapter in book (Other academic)
  • 31.
    Moparthi, Vamsi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Li, Xin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Vavitsas, Konstantinos
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Univ Copenhagen, Dept Plant & Environm Sci, CPSC, Thorvaldsensvej 40, DK-1871 Frederiksberg C, Denmark.
    Dzhygyr, Ievgen
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Umea Univ, Dept Mol Biol, 6K & 6L Sjukhusomradet, S-90187 Umea, Sweden.
    Sandh, Gustaf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Stockholm Univ, Dept Ecol Environm & Plant Sci, SciLifeLab, Box 1031, S-17121 Solna, Sweden.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    The two Dps proteins, NpDps2 and NpDps5, are involved in light-induced oxidative stress tolerance in the N2-fixing cyanobacterium Nostoc punctiforme2016In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1857, p. 1766-1776Article in journal (Refereed)
    Abstract [en]

    Cyanobacteria are photosynthetic prokaryotes that are considered biotechnologically prominent organisms for production of high-value compounds. Cyanobacteria are subject to high-light intensities, which is a challenge that needs to be addressed in design of efficient bio-engineered photosynthetic organisms. Dps proteins are members of the ferritin superfamily and are omnipresent in prokaryotes. They play a major role in oxidative stress protection and iron homeostasis. The filamentous, heterocyst-forming Nostoc punctiforme, has five Dps proteins. In this study we elucidated the role of these Dps proteins in acclimation to high light intensity, the gene loci organization and the transcriptional regulation of all five dps genes in N. punctiforme was revealed, and dps-deletion mutant strains were used in physiologica characterization. Two mutants defective in Dps2 and Dps5 activity displayed a reduced fitness under increased illumination, as well as a differential Photosystem (PS) stoichiometry, with an elevated Photosystem II to Photosystem I ratio in the dps5 deletion strain. This work establishes a Dps-mediated link between light tolerance,H2O2 detoxification, and iron homeostasis, and provides further evidence on the non-redundant role of multiple Dps proteins in this multicellular cyanobacterium.

  • 32.
    Németh, Brigitta
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Land, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hofer, Anders
    Institutionen för medicinsk kemi och biofysik, Umeå Universitet .
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Studying [FeFe] hydrogenase maturation and the nature of the HydF-HydA interactionManuscript (preprint) (Other academic)
  • 33.
    Ow, Saw Yen
    et al.
    Department of Chemical and Process Engineering, The University of Sheffield.
    Cardona, Tanai
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Taton, Arnaud
    Virginia Commonwealth University.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Wright, Philip C
    Department of Chemical and Process Engineering, The University of Sheffield.
    Quantitative shotgun proteomics of enriched heterocysts from Nostoc sp. PCC 7120 using 8-Plex isobaric peptide tags2008In: Journal of Proteome Research, ISSN 1535-3893, E-ISSN 1535-3907, Vol. 7, no 4, p. 1615-1628Article in journal (Refereed)
    Abstract [en]

    The filamentous cyanobacterium Nostoc sp. strain PCC 7120 is capable of fixing atmospheric nitrogen. The labile nature of the core process requires the terminal differentiation of vegetative cells to form heterocysts, specialized cells with altered cellular and metabolic infrastructure to mediate the N2-fixing process. We present an investigation targeting the cellular proteomic expression of the heterocysts compared to vegetative cells of a population cultured under N2-fixing conditions. New 8-plex iTRAQ reagents were used on enriched replicate heterocyst and vegetative cells, and replicate N2-fixing and non-N2-fixing filaments to achieve accurate measurements. With this approach, we successfully identified 506 proteins, where 402 had confident quantifications. Observations provided by purified heterocyst analysis enabled the elucidation of the dominant metabolic processes between the respective cell types, while emphasis on the filaments enabled an overall comparison. The level of analysis provided by this investigation presents various tools and knowledge that are important for future development of cyanobacterial biohydrogen production.

  • 34.
    Raleiras, Patricia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Kellers, P.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Evidence for non-cysteinyl coordination of the iron-sulfur clusters of HupS, the small subunit of the uptake hydrogenase from Nostoc punctiforme2014In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 19, p. S259-S259Article in journal (Other academic)
  • 35.
    Raleiras, Patricia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Kellers, Petra
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Isolation and Characterization of the Small Subunit of the Uptake Hydrogenase from the Cyanobacterium Nostoc punctiforme.2013In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 288, no 25, p. 18345-18352Article in journal (Refereed)
    Abstract [en]

     In nitrogen-fixing cyanobacteria, hydrogen evolution is associated with hydrogenases and nitrogenase, making these enzymes interesting targets for genetic engineering aimed at increased hydrogen production. Nostoc punctiforme ATCC 29133 is a filamentous cyanobacterium that expresses the uptake hydrogenase HupSL in heterocysts under nitrogen-fixing conditions. Little is known about the structural and biophysical properties of HupSL. The small subunit, HupS, has been postulated to contain three iron-sulfur clusters, but the details regarding their nature have been unclear due to unusual cluster binding motifs in the amino acid sequence. We now report the cloning and heterologous expression of Nostoc punctiforme HupS as a fusion protein, f-HupS. We have characterized the anaerobically purified protein by UV-visible and EPR spectroscopies. Our results show that f-HupS contains three iron-sulfur clusters. UV-visible absorption of f-HupS has bands similar to 340 and 420 nm, typical for iron-sulfur clusters. The EPR spectrum ofthe oxidized f-HupS shows a narrow g = 2.023 resonance, characteristic of a low-spin (S = 1/2) [3Fe-4S] cluster. The reduced f-HupS presents complex EPR spectra with overlapping resonances centered on g = 1.94, g = 1.91, and g = 1.88, typical of low-spin (S = 1/2) [4Fe-4S] clusters. Analysis of the spectroscopic data allowed us to distinguish between two species attributable to two distinct [4Fe-4S] clusters, in addition to the [3Fe-4S] cluster. This indicates that f-HupS binds [4Fe-4S] clusters despite the presence of unusual coordinating amino acids. Furthermore, our expression and purification of what seems to be an intact HupS protein allows future studies on the significance of ligand nature on redox properties ofthe iron-sulfur clusters of HupS.

  • 36.
    Raleiras, Patrícia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Photoinduced reduction of the medial FeS center in the hydrogenase small subunit HupS from Nostoc punctiforme2015In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 148, p. 57-61Article in journal (Refereed)
    Abstract [en]

    The small subunit from the NiFe uptake hydrogenase, HupSL, in the cyanobacterium Nostoc punctiforme ATCC 29133, has been isolated in the absence of the large subunit (P. Raleiras, P. Kellers, P. Lindblad, S. Styring, A. Magnuson, J. Biol. Chem. 288 (2013) 18,345-18,352). Here, we have used flash photolysis to reduce the iron-sulfur clusters in the isolated small subunit, HupS. We used ascorbate as electron donor to the photogenerated excited state of Ru(II)-trisbipyridine (Ru(bpy)3), to generate Ru(I)(bpy)3 as reducing agent. Our results show that the isolated small subunit can be reduced by the Ru(I)(bpy)3 generated through flash photolysis.

  • 37.
    Raleiras, Patrícia
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Khanna, Namita
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Miranda, Helder
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Meszaros, Livia S.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Krassen, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ho, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Battchikova, Natalia
    Turku University.
    Aro, Eva-Mari
    Turku University.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Turning around the electron flow in an uptake hydrogenase. EPR spectroscopy and in vivo activity of a designed mutant in HupSL from Nostoc punctiforme2016In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, no 2, p. 581-594Article in journal (Refereed)
    Abstract [en]

    The filamentous cyanobacterium Nostoc punctiforme ATCC 29133 produces hydrogen via nitrogenase in heterocysts upon onset of nitrogen-fixing conditions. N. punctiforme expresses concomitantly the uptake hydrogenase HupSL, which oxidizes hydrogen in an effort to recover some of the reducing power used up by nitrogenase. Eliminating uptake activity has been employed as a strategy for net hydrogen production in N. punctiforme (Lindberg et al., Int. J. Hydrogen Energy, 2002, 27, 1291-1296). However, nitrogenase activity wanes within a few days. In the present work, we modify the proximal iron-sulfur cluster in the hydrogenase small subunit HupS by introducing the designed mutation C12P in the fusion protein f-HupS for expression in E. coli (Raleiras et al., J. Biol. Chem., 2013, 288, 18345-18352), and in the full HupSL enzyme for expression in N. punctiforme. C12P f-HupS was investigated by EPR spectroscopy and found to form a new paramagnetic species at the proximal cluster site consistent with a [4Fe-4S] to [3Fe-4S] cluster conversion. The new cluster has the features of an unprecedented mixed-coordination [3Fe-4S] metal center. The mutation was found to produce stable protein in vitro, in silico and in vivo. When C12P HupSL was expressed in N. punctiforme, the strain had a consistently higher hydrogen production than the background [capital Delta]hupSL mutant. We conclude that the increase in hydrogen production is due to the modification of the proximal iron-sulfur cluster in HupS, leading to a turn of the electron flow in the enzyme.

  • 38. Rova, Maria
    et al.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Fredriksson, P.-O.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Coupled activation of the donor and acceptor side of photosystem II during activation of the oxygen evolving cluster1998In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 37, p. 11039-11045Article in journal (Refereed)
    Abstract [en]

    Photoactivation of photosystem II has been studied in the FUD 39 mutant of Chlamydomonas reinhardtii that lacks the 23 kDa extrinsic subunit of photosystem II. We have taken advantage of the slow photoactivation rate of FUD 39, earlier demonstrated in Rova, E. M., et al. [(1996) J. Biol. Chem. 271, 28918-28924], to study events in photosystem II during intermediate stages of the process. By measuring the EPR multiline signal, the decay of the variable fluorescence after single flashes, and electron transfer from water to the Q(B) site, we found a good correlation between the building of a tetrameric Mn cluster, longer recombination times between Q(A)(-) and the donor side of photosystem II, and the achievement of water splitting ability. An increased rate of electron transfer from Q(A)(-) to the Q(B) Site on the acceptor side of photosystem II, mainly due to enhanced efficiency of binding of Q(B) to its Site, was found to precede the building of the Mn cluster. We also showed that Tyro was oxidized simultaneously with this increase in electron-transfer rate. Thus, it appears that photoactivation is sequential, with an increased rate of electron transfer on the acceptor side occurring together with the oxidation of Tyro in the first step, followed by the assembly of the Mn cluster. We suggest that a conformational change of photosystem II is induced early in the photoactivation process facilitating electron transfer from the primary donor to the acceptor side. As a consequence, Tyr(D), an auxiliary electron donor to P-680(+)/Tyr(z)(.), is oxidized. That this occurs before the Mn cluster is fully functional serves to protect photosystem II against donor side induced photodamage.

  • 39. Rozman Grinberg, Inna
    et al.
    Berglund, Sigrid
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hasan, Mahmudul
    Lundin, Daniel
    Ho, Felix M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Logan, Derek T.
    Sjöberg, Britt-Marie
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Class Id ribonucleotide reductase utilizes a Mn2(IV,III) cofactor and undergoes large conformational changes on metal loading2019In: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 24, no 6, p. 863-877Article in journal (Refereed)
    Abstract [en]

    Outside of the photosynthetic machinery, high-valent manganese cofactors are rare in biology. It was proposed that a recently discovered subclass of ribonucleotide reductase (RNR), class Id, is dependent on a Mn2(IV,III) cofactor for catalysis. Class I RNRs consist of a substrate-binding component (NrdA) and a metal-containing radical-generating component (NrdB). Herein we utilize a combination of EPR spectroscopy and enzyme assays to underscore the enzymatic relevance of the Mn2(IV,III) cofactor in class Id NrdB from Facklamia ignava. Once formed, the Mn2(IV,III) cofactor confers enzyme activity that correlates well with cofactor quantity. Moreover, we present the X-ray structure of the apo- and aerobically Mn-loaded forms of the homologous class Id NrdB from Leeuwenhoekiella blandensis, revealing a dimanganese centre typical of the subclass, with a tyrosine residue maintained at distance from the metal centre and a lysine residue projected towards the metals. Structural comparison of the apo- and metal-loaded forms of the protein reveals a refolding of the loop containing the conserved lysine and an unusual shift in the orientation of helices within a monomer, leading to the opening of a channel towards the metal site. Such major conformational changes have not been observed in NrdB proteins before. Finally, in vitro reconstitution experiments reveal that the high-valent manganese cofactor is not formed spontaneously from oxygen, but can be generated from at least two different reduced oxygen species, i.e. H2O2 and superoxide (O 2 ·− ). Considering the observed differences in the efficiency of these two activating reagents, we propose that the physiologically relevant mechanism involves superoxide.

  • 40.
    Schmitt, Heimo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Lomoth, Reiner
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Park, Jonathan
    Fryxelius, Jacob
    Kritikos, Mikael
    Mårtensson, Jerker
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Åkermark, Björn
    Synthesis, Redix Properties, and EPR Spectroscopy of Manganese(III) Complexes of Ligand N,N-Bis(2-hydroxybenzyl)-N'-2-hydroxybenzylidene-1,2-diaminoethane: Formation of Mononuclear, Dinuclear, and even Higher Nuclearity Complexes2002In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 8, no 16, p. 3757-3768Article in journal (Refereed)
    Abstract [en]

    The synthesis and characterization of the title trisphenolate ligand are described. From its reaction with manganese(iii) three complexes were isolated. The crystal structures revealed one pentacoordinate monomer and two similar dimers with different solvents of crystallization. In the dimers the metal ions are hexacoordinate and connected through bridging of two phenolates. A combination of electrochemistry and EPR spectroscopy showed that, in acetonitrile, the isolated batches were all identical and mainly monomeric, indicating that the mononuclear complex is in equilibrium with the dimer and perhaps also with complexes of higher nuclearity, as suggested by the detection of both the trimer and the tetramer by electrospray ionization mass spectrometry (ESI-MS). The successful use of the monomer batch as an epoxidation catalyst indicated that a high-valent manganese-oxo species can be formed, although it is probably short-lived. This is also suggested by EPR studies of the species formed by electrochemical oxidation of the complex. Upon one-electron oxidation, a manganese(iv) species was formed, which was at least partly converted to another species containing a phenoxy radical.

  • 41. Sun, Licheng
    et al.
    Burkitt, Mark
    Tamm, Markus
    Raymond, Mary Kathrine
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Abrahamsson, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    LeGourriérec, Denis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Frapart, Yves
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Brandt, Peter
    Tran, Ahn
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Åkermark, Björn
    Hydrogen-Bond Promoted Intramolecular Electron Transfer to Photogenerated Ru(III): A Functional Mimic of TyrosineZ and Histidine 190 in Photosystem II1999In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 121, no 29, p. 6834-6842Article in journal (Refereed)
    Abstract [en]

    As a model for redox components on the donor side of photosystem II (PS II) in green plants, a supramolecular complex 4 has been prepared. In this, a ruthenium(II) tris-bipyridyl complex which mimics the function of P680 in PS II, has been covalently linked to a tyrosine unit which bears two hydrogen-bonding substituents, dipicolylamine (dpa) ligands. Our aim is to mimic the interaction between tyrosineZ and a basic histidine residue, namely His190 in PSII, and also to use the dpa ligands for coordination of manganese. Two different routes for the synthesis of the compound 4 are presented. Its structure was fully characterized by 1H NMR, COSY, NOESY, 13C NMR, IR, and mass spectrometry. 1H NMR and NOESY gave evidence for the existence of intramolecular hydrogen bonding in 4. The interaction between the ruthenium and the substituted tyrosine unit was probed by steady-state and time-resolved emission measurements as well as by chemical oxidation. Flash photolysis and EPR measurements on 4 in the presence of an electron acceptor (methylviologen, MV2+, or cobalt pentaminechloride, Co3+) showed that an intermolecular electron transfer from the excited state of Ru(II) in 4 to the electron acceptor took place, forming Ru(III) and the methylviologen radical MV+ or Co2+. This was followed by intramolecular electron transfer from the substituted tyrosine moiety to the photogenerated Ru(III), regenerating Ru(II) and forming a tyrosyl radical. In water, the radical has a g value of 2.0044, indicative of a deprotonated tyrosyl radical. In acetonitrile, a radical with a g value of 2.0029 was formed, which can be assigned to the tyrosine radical cation. In both solvents the electron transfer is intramolecular with a rate constant kET > 1 × 107 s-1. This is 2 orders of magnitude greater than the one for a similar compound 3, in which no dpa arm is attached to the tyrosine unit. Therefore the hydrogen bonding between the substituted tyrosine and the dpa arms in 4 is proposed to be responsible for the fast electron transfer. This interaction mimics the proposed His190 and tyrosineZ interaction in the donor side of PS II.

  • 42. Sun, Licheng
    et al.
    Raymond, Mary Katherine
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Magnuson, Ann
    LeGourriérec, Denis
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Tamm, Markus
    Abrahamsson, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Huang Kenéz, Ping
    Mårtensson, Jerker
    Stenhagen, G.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Åkermark, Björn
    Towards an artificial model for Photosystem II: A manganese(II,II) dimer covalently linked to ruthenium(II) tris-bipyridine via a tyrosine derivative2000In: Journal of Inorganic Biochemistry, ISSN 0162-0134, E-ISSN 1873-3344, Vol. 78, no 1, p. 15-22Article in journal (Refereed)
    Abstract [en]

    In order to model the individual electron transfer steps from the manganese cluster to the photooxidized sensitizer P680+ in Photosystem II (PS II) in green plants, the supramolecular complex 4 has been synthesized. In this complex, a ruthenium(II) tris-bipyridine type photosensitizer has been linked to a manganese(II) dimer via a substituted L-tyrosine, which bridges the manganese ions. The trinuclear complex 4 was characterized by electron paramagnetic resonance (EPR) and electrospray ionization mass spectrometry (ESI-MS). The excited state lifetime of the ruthenium tris-bipyridine moiety in 4 was found to be about 110 ns in acetonitrile. Using flash photolysis in the presence of an electron acceptor (methylviologen), it was demonstrated that in the supramolecular complex 4 an electron was transferred from the excited state of the ruthenium tris-bipyridine moiety to methylviologen, forming a methylviologen radical and a ruthenium(III) tris-bipyridine moiety. Next, the Ru(III) species retrieved the electron from the manganese(II/II) dimer in an intramolecular electron transfer reaction with a rate constant kET > 1.0 x 10(7) s(-1), generating a manganese(II/III) oxidation state and regenerating the ruthenium(II) photosensitizer. This is the first example of intramolecular electron transfer in a supramolecular complex, in which a manganese dimer is covalently linked to a photosensitizer via a tyrosine unit, in a process which mimics the electron transfer on the donor side of PS II.

  • 43.
    Thapper, Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Saracco, Guido
    Politecnico di Torino, Torino.
    Rutherford, A. William
    Imperial College, London.
    Robert, Bruno
    Institute of Biology and Technology of Saclay, CEA, CNRS and Université Paris Sud, Gif sur Yvette.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Lubitz, Wolfgang
    Max Planck Institute for Chemical Energy Conversion, Mülheim/Ruhr.
    Llobet, Antoni
    Institute of Chemical Research of Catalonia (ICIQ ), Tarragona.
    Kurz, Philipp
    Albert-Ludwigs-University Freiburg, Freiburg.
    Holzwarth, Alfred
    Max Planck Institute for Chemical Energy Conversion, Mülheim/Ruhr.
    Fiechter, Sebastian
    Helmholtz Zentrum Berlin für Materialien und Energie GmbH, Institute for Solar Fuels, Berlin.
    de Groot, Huub
    Leiden University, Leiden.
    Campagna, Sebastiano
    University of Messina, Messina.
    Braun, Artur
    Swiss Federal Laboratories for Materials Science and Technology; Dübendorf.
    Bercegol, Hervé
    CEA/DSM, Alternative Energies and Atomic Energy Commission, CEA Saclay.
    Artero, Vincent
    Université Joseph Fourier, CEA, Grenoble.
    Artificial Photosynthesis for Solar Fuels – an Evolving Research Field within AMPEA, a Joint Programme of the European Energy Research Alliance2013In: Green, Vol. 3, no 1, p. 43-57Article in journal (Refereed)
    Abstract [en]

    On the path to an energy transition away from fossil fuels to sustainable sources, the European Union is for the moment keeping pace with the objectives of the Strategic Energy Technology-Plan. For this trend to continue after 2020, scientific breakthroughs must be achieved. One main objective is to produce solar fuels from solar energy and water in direct processes to accomplish the efficient storage of solar energy in a chemical form. This is a grand scientific challenge. One important approach to achieve this goal is Artificial Photosynthesis. The European Energy Research Alliance has launched the Joint Programme “Advanced Materials & Processes for Energy Applications” (AMPEA) to foster the role of basic science in Future Emerging Technologies. European researchers in artificial photosynthesis recently met at an AMPEA organized workshop to define common research strategies and milestones for the future. Through this work artificial photosynthesis became the first energy research sub-field to be organised into what is designated “an Application” within AMPEA. The ambition is to drive and accelerate solar fuels research into a powerful European field – in a shorter time and with a broader scope than possible for individual or national initiatives. Within AMPEA the Application Artificial Photosynthesis is inclusive and intended to bring together all European scientists in relevant fields. The goal is to set up a thorough and systematic programme of directed research, which by 2020 will have advanced to a point where commercially viable artificial photosynthetic devices will be under development in partnership with industry.

  • 44.
    Wennman, Anneli
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Jernerén, Fredrik
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Oliw, Ernst H
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences. Uppsala University, BMC.
    Expression and characterization of manganese lipoxygenase of the rice blast fungus reveals prominent sequential lipoxygenation of α-linolenic acid2015In: Archives of Biochemistry and Biophysics, ISSN 0003-9861, E-ISSN 1096-0384, Vol. 583, p. 87-95Article in journal (Refereed)
    Abstract [en]

    Magnaporthe oryzae causes rice blast disease and has become a model organism of fungal infections. M. oryzae can oxygenate fatty acids by 7,8-linoleate diol synthase, 10R-dioxygenase-epoxy alcohol synthase, and by a putative manganese lipoxygenase (Mo-MnLOX). The latter two are transcribed during infection. The open reading frame of Mo-MnLOX was deduced from genome and cDNA analysis. Recombinant Mo-MnLOX was expressed in Pichia pastoris and purified to homogeneity. The enzyme contained protein-bound Mn and oxidized 18:2n-6 and 18:3n-3 to 9S-, 11-, and 13R-hydroperoxy metabolites by suprafacial hydrogen abstraction and oxygenation. The 11-hydroperoxides were subject to β-fragmentation with formation of 9S- and 13R-hydroperoxy fatty acids. Oxygen consumption indicated apparent kcat values of 2.8 s(-1) (18:2n-6) and 3.9 s(-1) (18:3n-3), and UV analysis yielded apparent Km values of 8 and 12 μM, respectively, for biosynthesis of cis-trans conjugated metabolites. 9S-Hydroperoxy-10E,12Z,15Z-octadecatrienoic acid was rapidly further oxidized to a triene, 9S,16S-dihydroperoxy-10E,12Z,14E-octadecatrienoic acid. In conclusion, we have expressed, purified and characterized a new MnLOX from M. oryzae. The pathogen likely secretes Mo-MnLOX and phospholipases to generate oxylipins and to oxidize lipid membranes of rice cells and the cuticle.

  • 45.
    Wennman, Anneli
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Hamberg, Mats
    Oliw, Ernst H.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmaceutical Biosciences.
    Manganese lipoxygenase of F. oxysporum and the structural basis for biosynthesis of distinct 11-hydroperoxy stereoisomers2015In: Journal of Lipid Research, ISSN 0022-2275, E-ISSN 1539-7262, Vol. 56, no 8, p. 1606-1615Article in journal (Refereed)
    Abstract [en]

    The biosynthesis of jasmonates in plants is initiated by 13S-lipoxygenase (LOX), but details of jasmonate biosynthesis by fungi, including Fusarium oxysporum, are unknown. The genome of F. oxysporum codes for linoleate 13S-LOX (Fox-LOX) and for F. oxysporum manganese LOX (Fo-MnLOX), an uncharacterized homolog of 13R-MnLOX of Gaeumannomyces graminis. We expressed Fo-MnLOX and compared its properties to Cg-MnLOX from Colletotrichum gloeosporioides. Electron paramagnetic resonance and metal analysis showed that Fo-MnLOX contained catalytic Mn. Fo-MnLOX oxidized 18:2n-6 mainly to 11 R-hydroperoxyoctadecadienoic acid (HPODE), 13S-HPODE, and 9(S/R)-HPODE, whereas Cg-MnLOX produced 9S-, 11S-, and 13R-HPODE with high stereoselectivity. The 11-hydroperoxides did not undergo the rapid beta-fragmentation earlier observed with 13R-MnLOX. Oxidation of [11S-H-2] 18:2n-6 by Cg-MnLOX was accompanied by loss of deuterium and a large kinetic isotope effect (>30). The Fo-MnLOX-catalyzed oxidation occurred with retention of the H-2-label. Fo-MnLOX also oxidized 1-lineoyl-2-hydroxy-glycero3- phosphatidylcholine. The predicted active site of all MnLOXs contains Phe except for Ser(348) in this position of Fo-MnLOX. The Ser348Phe mutant of Fo-MnLOX oxidized 18: 2n-6 to the same major products as Cg-MnLOX.Jlr Our results suggest that Fo-MnLOX, with support of Ser(348), binds 18:2n-6 so that the pro R rather than the proShydrogen at C-11 interacts with the metal center, but retains the suprafacial oxygenation mechanism observed in other MnLOXs.

  • 46. Xu, Yunhua
    et al.
    Eilers, Gerriet
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Borgström, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Pan, Jingxi
    Abrahamsson, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Magnuson, Ann
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Lomoth, Reiner
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Polivka, Tomas
    Sun, Licheng
    Sundström, Villy
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Åkerman, Björn
    Synthesis and characterization of dinuclear ruthenium complexes covalently linked to Ru(II) tris-bipyridine: an approach to mimics of the donor side of photosystem II2005In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 11, no 24, p. 7305-7314Article in journal (Refereed)
    Abstract [en]

    The structural rearrangements triggered by oxidation of the dinuclear Mn complex [Mn2(bpmp)(u-OAc)2]+ (bpmp = 2,6-bis[bis(2-pyridylmethyl)amino]methyl-4-methylphenol anion) in the presence of water have been studied by combinations of electrochemistry with IR spectroscopy and with electrospray ionization mass spectrometry (ESI-MS). The exchange of acetate bridges for water (D2O) derived ligands in different oxidation states could be monitored by mid-IR spectroscopy in CD3CN-D2O mixtures following the Vas(C-O) bands of bound acetate at 1594.4 cm-1 (II,II), 1592.0 cm-1 (II,III) and 1586.5 cm-1 (III,III). Substantial loss of bound acetate occurs at much lower water content (<0.5% v/v) in the III,III state than in the II,II and II,III states (>10%). The ligand-exchange reactions do not initially reduce the overall charge of the complex but facilitate further oxidation by proton-coupled electron transfer as the water-derived ligands are increasingly deprotonated in higher oxidation states. In the IR spectra deprotonation could be followed by the formation of acetic acid (DOAc, ~1725 cm-1, V(C-O)) from the released acetate (1573.6 cm-1, Vas(C-O)). By the on-line combination of an electrochemical flow cell with ESI-MS several product complexes could be identified. A di-u-oxo bridged III,IV dimer [Mn2(bpmp)(u-O)2]2+ (m/z 335.8) can be generated at potentials below the III,III/II,III couple of the di-u-acetato complex (0.61 V Vs. ferrocene). The ligand-exchange reactions allow for three metal-centered oxidation steps to occur from II,II to III,IV in a potential range of only 0.5 V, explaining the formation of a spin-coupled III,IV dimer by photo-oxidation with [Ru(bpy)3]3+ in previous EPR studies.

1 - 46 of 46
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf