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  • 1.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Becker, Hans-Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Bonnefous, Celine
    Chamchoumis, Charles
    Thummel, Randolph
    Six-membered Ring Chelate Complexes of Ru(II): Structural and photophysical effects2007In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 46, no 24, p. 10354-10364Article in journal (Refereed)
    Abstract [en]

    The structural and photophysical properties of Ru(II)−polypyridyl complexes with five- and six-membered chelate rings were studied for two bis-tridentate and two tris-bidentate complexes. The photophysical effect of introducing a six-membered chelate ring is most pronounced for the tridentate complex, leading to a room-temperature excited-state lifetime of 810 ns, a substantial increase from 180 ns for the five-membered chelate ring model complex. Contrasting this, the effect is the opposite in tris-bidentate complexes, in which the lifetime decreases from 430 ns to around 1 ns in going from a five-membered to six-membered chelate ring. All of the complexes were studied spectroscopically at both 80 K and ambient temperatures, and the temperature dependence of the excited-state lifetime was investigated for both of the bis-tridentate complexes. The main reason for the long excited-state lifetime in the six-membered chelate ring bis-tridentate complex was found to be a strong retardation of the activated decay via metal-centered states, largely due to an increased ligand field splitting due to the complex having a more-octahedral geometry.

  • 2.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Tocher, Derek
    Nag, Samik
    Datta, Dipankar
    Modulation of the lowest metal-to-ligand charge-transfer state in [Ru(bpy)(2)(N-N)](2+) systems by changing the N-N from hydrazone to azine: Photophysical Consequences2006In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, no 23, p. 9580-9586Article in journal (Refereed)
    Abstract [en]

    Two Ru( II) complexes, [ Ru( bpy) L-2]( ClO4) 2 ( 1) and [ Ru( bpy)(2)L']( BF4) 2 ( 2), where bpy is 2,2'-bipyridine, L is diacetyl dihydrazone, and L' 1: 2 is the condensate of L and acetone, are synthesized. From X-ray crystal structures, both are found to contain distorted octahedral RuN62+ cores. NMR spectra show that the cations in 1 and 2 possess a C-2 axis in solution. They display the expected metal-to-ligand charge transfer ( (MLCT)-M-1) band in the 400 - 500 nm region. Complex 1 is nonemissive at room temperature in solution as well as at 80 K. In contrast, complex 2 gives rise to an appreciable emission upon excitation at 440 nm. The room-temperature emission is centered at 730 nm ( lambda(max)(em)) with a quantum yield ( em) of 0.002 and a lifetime ( tau(em)) of 42 ns in an air-equilibrated methanol - ethanol solution. At 80 K, Phi(em) = 0.007 and tau(em)= 178 ns, with a lambda(max)(em) of 690 nm, which is close to the 0 - 0 transition, indicating an (MLCT)-M-3 excited-state energy of 1.80 eV. The radiative rate constant ( 5 x 10(4) s(-1)) at room temperature and 80 K is almost temperature independent. From spectroelectrochemistry, it is found that bpy is easiest to reduce in 2 and that L is easiest in 1. The implications of this are that in 2 the lowest (MLCT)-M-3 state is localized on a bpy ligand and in 1 it is localized on L. Transient absorption results also support these assignments. As a consequence, even though 2 shows a fairly strong and long-lived emission from a Ru( II) -> bpy CT state, the Ru( II) -> L CT state in 1 shows no detectable emission even at 80 K.

  • 3. Abrahamsson, Maria
    et al.
    Hedberg, Joachim H. J.
    Becker, Hans-Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Staniszewski, Aaron
    Pearson, Wayne H.
    Heuer, William B.
    Meyer, Gerald J.
    High Extinction Coefficient Ru-Sensitizers that Promote Hole Transfer on Nanocrystalline TiO22014In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 6, p. 1154-1163Article in journal (Refereed)
    Abstract [en]

    Two series of Ru-II polypyridyl compounds with formulas [(bpy)(2)RuL](PF6)(2) and [(deeb)(2)RuL](PF6)(2), where bpy is 2,2-bipyridine, deeb is 4,4-diethylester-2,2-bpy, and L is one of several substituted 9-(1,3-dithiole-2-ylidene)-4,5-diazafluorene ligands, were studied as potential photosensitizers for TiO2. These compounds possess notably high extinction coefficients (40000M(-1)cm(-1) @470 nm) which are shown by time-dependent density functional theory (TD-DFT) calculations to result from overlapping metal-to-ligand charge transfer (MLCT) and ligand-localized transitions. Low-temperature absorption and photoluminescence measurements were suggestive of a short-lived MLCT excited state. When adsorbed onto TiO2 thin films, both the free ligands (L) and their corresponding [(deeb)(2)RuL](2+) complexes exhibited rapid excited-state electron injection into TiO2; in the case of the complexes, this was followed by rapid (k>10(8) s(-1)) hole transfer from Ru-III to the 1,3-dithiole ring of the L ligand. Observation of diffusion-limited reductive quenching of the [Ru(bpz)(3)](2+)* (bpz is 2,2-bipyrazine) excited state by the L ligands in solution supported the occurrence of intramolecular hole transfer following electron injection by the TiO2-anchored complexes.

  • 4.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Accelerator mass spectrometry group. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Jäger, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Kumar, Rohan J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Österman, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Persson, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Becker, Hans-Christian
    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 Quantum Chemistry.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Bistridentate Ruthenium(II)polypyridyl-Type Complexes with Microsecond 3MLCT State Lifetimes: Sensitizers for Rod-Like Molecular Arrays2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 46, p. 15533-15542Article in journal (Refereed)
    Abstract [en]

    A series of bistridentate ruthenium(II) polypyridyl-type complexes based on the novel 2,6-di(quinolin-8-yl)pyridine (dqp) ligand have been synthesized and their photophysical properties have been studied. The complexes are amenable to substitution in the 4-position of the central pyridine with conserved quasi-C2v symmetry, which allows for extension to isomer-free, rod-like molecular arrays for vectorial control of electron and energy transfer. DFT calculations performed on the parent [Ru(dqp) 2](2+) complex (1) predicted a more octahedral structure than in the typical bistridentate complex [Ru(tpy)2](2+) (tpy is 2,2':6',2"-terpyridine) thanks to the larger ligand bite angle, which was confirmed by X-ray crystallography. A strong visible absorption band, with a maximum at 491 nm was assigned to a metal-to-ligand charge transfer (MLCT) transition, based on time-dependent DFT calculations. 1 shows room temperature emission (Phi = 0.02) from its lowest excited ((3)MLCT) state that has a very long lifetime (tau = 3 micros). The long lifetime is due to a stronger ligand field, because of the more octahedral structure, which makes the often dominant activated decay via short-lived metal-centered states insignificant also at elevated temperatures. A series of complexes based on dqp with electron donating and/or accepting substituents in the 4-position of the pyridine was prepared and the properties were compared to those of 1. An unprecedented (3)MLCT state lifetime of 5.5 micros was demonstrated for the homoleptic complex based on dqpCO2Et. The favorable photosensitizer properties of 1, such as a high extinction coefficient, high excited-state energy and long lifetime, and tunable redox potentials, are maintained upon substitution. In addition, the parent complex 1 is shown to be remarkably photostable and displays a high reactivity in light-induced electron and energy transfer reactions with typical energy and electron acceptors and donors: methylviologen, tetrathiofulvalene, and 9,10-diphenylanthracene. This new class of complexes constitutes a promising starting point for the construction of linear, rod-like molecular arrays for photosensitized reactions and applications in artificial photosynthesis and molecular electronics.

  • 5.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, För teknisk-naturvetenskapliga fakulteten gemensamma enheter, Accelerator mass spectrometry group. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Jäger, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Österman, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Eriksson, Lars
    Persson, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Becker, Hans-Christian
    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.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    A 3.0 mu s room temperature excited state lifetime of a bistridentate Ru-II-polypyridine complex for rod-like molecular arrays2006In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, no 39, p. 12616-12617Article in journal (Refereed)
    Abstract [en]

    A bistridentate RuII-polypyridine complex [Ru(bqp)2]2+ (bqp = 2,6-bis(8'-quinolinyl)pyridine) has been prepared, which has a coordination geometry much closer to a perfect octahedron than the typical Ru(terpyridine)2-type complex. Thus, the complex displays a 3.0 mus lifetime of the lowest excited metal-to-ligand charge transfer (3MLCT) state at room temperature. This is, to the best of our knowledge, the longest MLCT state lifetime reported for a RuII-polypyridyl complex at room temperature. The structure allows for the future construction of rod-like, isomer-free molecular arrays by substitution of donor and acceptor moieties on the central pyridine units. This makes it a promising photosensitizer for applications in molecular devices for artificial photosynthesis and molecular electronics.

  • 6.
    Abrahamsson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lundqvist, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Wolpher, Henriette
    Johansson, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Eriksson, Lars
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Analytical Chemistry.
    Rasmussen, Torben
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry.
    Becker, Hans-Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Norrby, Per-Ola
    Åkermark, Björn
    Persson, Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Quantum Chemistry.
    Steric influence on the excited-state lifetimes of ruthenium complexes with bipyridyl-alkanylene-pyridyl ligands.2008In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 47, no 9, p. 3540-3548Article in journal (Refereed)
    Abstract [en]

    The structural effect on the metal-to-ligand charge transfer (MLCT) excited-state lifetime has been investigated in bis-tridentate Ru(II)-polypyridyl complexes based on the terpyridine-like ligands [6-(2,2'-bipyridyl)](2-pyridyl)methane (1) and 2-[6-(2,2'-bipyridyl)]-2-(2-pyridyl)propane (2). A homoleptic ([Ru(2)(2)](2+)) and a heteroleptic complex ([Ru(ttpy)(2)](2+)) based on the new ligand 2 have been prepared and their photophysical and structural properties studied experimentally and theoretically and compared to the results for the previously reported [Ru(1)(2)](2+). The excited-state lifetime of the homoleptic Ru-II complex with the isopropylene-bridged ligand 2 was found to be 50 times shorter than that of the corresponding homoleptic Ru-II complex of ligand 1, containing a methylene bridge. A comparison of the ground-state geometries of the two homoleptic complexes shows that steric interactions involving the isopropylene bridges make the coordination to the central Ru-II ion less octahedral in [Ru(2)(2)](2+) than in [Ru(1)(2))(2+). Calculations indicate that the structural differences in these complexes influence their ligand field splittings as well as the relative stabilities of the triplet metal-to-ligand charge transfer ((MLCT)-M-3) and metal-centered ((MC)-M-3) excited states. The large difference in measured excited-state lifetimes for the two homoleptic Ru-II complexes is attributed to a strong influence of steric interactions on the ligand field strength, which in turn affects the activation barriers for thermal conversion from (MLCT)-M-3 states to short-lived (MC)-M-3 states.

  • 7.
    Agervald, Åsa
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Maturation and Regulation of Cyanobacterial Hydrogenases2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Accelerated global warming plus an increasing need for energy is an equation not easily solved, thus new forms of sustainable energy production are urgently requested. In this context hydrogen production based on a cyanobacterial system offers an environmentally friendly alternative for energy capture and conversion. Cyanobacteria can produce hydrogen gas from sun light and water through the combination of photosystems and hydrogenases, and are suitable to cultivate in large scale.

    In the present thesis the maturation process of [NiFe]-hydrogenases is investigated with special focus on transcription of the accessory genes encoding proteins needed for assembly of the large and possibly also for the small hydrogenase subunit. The cyanobacteria used are two N2-fixing, filamentous, heterocystous strains; Nostoc sp. strain PCC 7120 and Nostoc punctiforme PCC 73102.

    For a biotechnological exploration of hydrogen production tools for regulatory purposes are important. The transcription factor CalA (cyanobacterial AbrB like) (Alr0946 in the genome) in Nostoc sp. strain PCC 7120 was found to be involved in hydrogen metabolism by regulating the transcription of the maturation protein HypC. Further the bidirectional hydrogenase activity was down-regulated in the presence of elevated levels of CalA, a result important to take into account when optimizing cyanobacteria for hydrogen production.

    CalA regulates at least 25 proteins in Nostoc sp. strain PCC 7120 and one of the down-regulated proteins was superoxide dismutase, FeSOD. The characterization of FeSOD shows that it has a specific and important function in the oxidative stress tolerance of Nostoc sp. stain PCC 7120. Since CalA is involved in regulation of both the hydrogen metabolism as well as stress responses these findings indicate that Alr0946 is an important transcription factor in Nostoc sp. strain PCC 7120 active on a global level in the cell.

    This thesis adds more knowledge concerning maturation and regulation of cyanobacterial hydrogenases which might be useful for future large scale hydrogen.

    List of papers
    1. The CyAbrB transcription factor Alr0946 regulates the iron superoxide dismutase in Nostoc sp. strain PCC 7120
    Open this publication in new window or tab >>The CyAbrB transcription factor Alr0946 regulates the iron superoxide dismutase in Nostoc sp. strain PCC 7120
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In the present investigation we analyse the results of induced over-production of the CyAbrB transcription factor Alr0946 in the cyanobacterium Nostoc sp. PCC 7120 with special focus on its effects on FeSOD. With gel based quantitative proteomics the induced over-expression of Alr0946 was shown to influence the abundance of at least 25 proteins. One of the proteins with a significant lower abundance was FeSOD, one of two types of superoxide dismutases in Nostoc sp. PCC 7120. The change in protein abundance was also followed by lower transcript as well as activity levels. Purified Alr0946 from Nostoc sp. PCC 7120 was shown to interact with the promoter region of alr2938, encoding FeSOD, indicating a transcriptional regulation of FeSOD by Alr0946. The Alr0946 over-expression strain showed a bleaching phenotype with lower growth rate and truncated filaments already two days after induction of over-expression. The phenotype was even more pronounced when illumination was increased from 35 to 125 μmol m-2s-1. This is in line with an increased need of FeSOD during a stronger oxidative stress. The results indicate that Alr0946 is involved in regulation of stress responses and that FeSOD has a specific and important function in the oxidative stress tolerance of the multicellular cyanobacterium Nostoc sp. PCC 7120.

    Keywords
    Nostoc sp. PCC 7120, FeSOD, Alr0946, transcription factor, CyAbrB
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-110862 (URN)
    Available from: 2009-11-27 Created: 2009-11-27 Last updated: 2016-04-21
    2. Transcription of the extended hyp-operon in Nostoc sp. strain PCC 7120
    Open this publication in new window or tab >>Transcription of the extended hyp-operon in Nostoc sp. strain PCC 7120
    2008 (English)In: BMC Microbiology, ISSN 1471-2180, E-ISSN 1471-2180, Vol. 8, p. 69-Article in journal (Refereed) Published
    Abstract [en]

    Background: The maturation of hydrogenases into active enzymes is a complex process and e. g. a correctly assembled active site requires the involvement of at least seven proteins, encoded by hypABCDEF and a hydrogenase specific protease, encoded either by hupW or hoxW. The N2fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain both an uptake and a bidirectional hydrogenase. The present study addresses the presence and expression of hypgenes in Nostoc sp. strain PCC 7120. Results: RTPCRs demonstrated that the six hypgenes together with one ORF may be transcribed as a single operon. Transcriptional start points (TSPs) were identified 280 bp upstream from hypF and 445 bp upstream of hypC, respectively, demonstrating the existence of several transcripts. In addition, five upstream ORFs located in between hupSL, encoding the small and large subunits of the uptake hydrogenase, and the hypoperon, and two downstream ORFs from the hypgenes were shown to be part of the same transcript unit. A third TSP was identified 45 bp upstream of asr0689, the first of five ORFs in this operon. The ORFs are annotated as encoding unknown proteins, with the exception of alr0692 which is identified as a NifUlike protein. Orthologues of the four ORFs asr0689alr0692, with a highly conserved genomic arrangement positioned between hupSL, and the hyp genes are found in several other N2fixing cyanobacteria, but are absent in non N2fixing cyanobacteria with only the bidirectional hydrogenase. Short conserved sequences were found in six intergenic regions of the extended hypoperon, appearing between 11 and 79 times in the genome. Conclusion: This study demonstrated that five ORFs upstream of the hypgene cluster are cotranscribed with the hypgenes, and identified three TSPs in the extended hypgene cluster in Nostoc sp. strain PCC 7120. This may indicate a function related to the assembly of a functional uptake hydrogenase, hypothetically in the assembly of the small subunit of the enzyme.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-110173 (URN)10.1186/1471-2180-8-69 (DOI)000256297500001 ()
    Available from: 2009-11-05 Created: 2009-11-05 Last updated: 2017-12-12
    3. CalA, a cyanobacterial AbrB protein, interacts with the upstream region of hypC and acts as a repressor of its transcription in the cyanobacterium Nostoc sp. strain PCC 7120
    Open this publication in new window or tab >>CalA, a cyanobacterial AbrB protein, interacts with the upstream region of hypC and acts as a repressor of its transcription in the cyanobacterium Nostoc sp. strain PCC 7120
    Show others...
    2010 (English)In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 76, no 3, p. 880-890Article in journal (Refereed) Published
    Abstract [en]

    The filamentous, heterocystous, nitrogen-fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain, depending on growth condition, up to two hydrogenases directly involved in hydrogen metabolism. HypC is one out of at least seven auxiliary gene products required for synthesis of a functional hydrogenase, specifically involved in the maturation of the large subunit. In this study we present a protein, Alr0946, belonging to the transcription regulator family AbrB, which in protein-DNA assays was found to interact with the upstream region of hypC. Transcriptional investigations showed that alr0946 is co-transcribed with the downstream gene alr0947, which encodes a putative protease from the abortive infection superfamily, Abi. Alr0946 was shown to interact specifically not only with the upstream region of hypC but also with its own upstream region, acting as a repressor on both. The bidirectional hydrogenase activity was significant down-regulated when Alr0946 was over-expressed demonstrating a correlation to the transcription factor, either direct or indirect. In silico studies showed that homologues to both Alr0946 and Alr0947 are highly conserved proteins within cyanobacteria with a very similar physical organisation of the corresponding structural genes. Possible functions of the co-transcribed downstream protein Alr0947 are presented. In addition, we present a 3D model of the CyAbrB domain of Alr0946 and putative DNA-binding mechanisms are discussed.

    Keywords
    Nostoc sp. strain PCC 7120, hypC, Alr0946, CyAbrB, hydrogen metabolism
    National Category
    Biological Sciences
    Identifiers
    urn:nbn:se:uu:diva-110863 (URN)10.1128/AEM.02521-09 (DOI)000274017400030 ()
    Available from: 2009-11-27 Created: 2009-11-27 Last updated: 2017-12-12
    4. Isolation and characterization of thylakoid membranes from the filamentous cyanobacterium Nostoc punctiforme
    Open this publication in new window or tab >>Isolation and characterization of thylakoid membranes from the filamentous cyanobacterium Nostoc punctiforme
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    2007 (English)In: 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) Published
    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.

    Keywords
    Nostoc punctiforme, isolation, membranes, thylakoids, proteomics, photosystem II, photosystem I
    National Category
    Chemical Sciences Biological Sciences
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:uu:diva-12478 (URN)10.1111/j.1399-3054.2007.00982.x (DOI)000250763500010 ()18251853 (PubMedID)
    Available from: 2012-05-08 Created: 2007-12-27 Last updated: 2017-12-11Bibliographically approved
    5. Transcript analysis of the extended hyp-operons in the cyanobacteria Nostoc sp. strain PCC 7120 and Nostoc punctiforme ATCC 29133
    Open this publication in new window or tab >>Transcript analysis of the extended hyp-operons in the cyanobacteria Nostoc sp. strain PCC 7120 and Nostoc punctiforme ATCC 29133
    Show others...
    2011 (English)In: BMC Research Notes, ISSN 1756-0500, E-ISSN 1756-0500, Vol. 4, no 186Article in journal (Other academic) Published
    Abstract [en]

    The ability of cyanobacteria to capture solar energy, via oxygenic photosynthesis, and convert that energy to molecular hydrogen (H2) has made them an interesting group of organisms with potential as future energy producers. There are three types of enzymes directly involved in the cyanobacterial hydrogen metabolism; nitrogenases that produce H2 as a by-product when fixating atmospheric nitrogen, uptake hydrogenases that catalyze the oxidation of H2,thereby preventing energy losses from the cells, and bidirectional hydrogenases that has the capacity to both oxidize and reduce H2. Hydrogenases are complex metalloenzymes, and the insertion of ligands and correct folding of the proteins require assistance of accessory proteins, the Hyp proteins. Cyanobacterial hydrogenases are NiFe-type hydrogenases and consist of a large and a small subunit. Today, the maturation process of the large subunit has been uncovered to a large extent in cyanobacteria, mostly by analogy assumptions from studies done in other bacteria such as Escherichia coli but also from mutational analyses in cyanobacteria, while the maturation process of the small subunit is still unknown. Recently a set of genes, putatively involved in the maturation process of the small subunit, was discovered in Nostoc sp. PCC 7120 and Nostoc punctiforme ATCC 29133. These five ORFs, encoding unknown proteins, are located in between the uptake hydrogenase structural genes and the hyp-genes were shown to be transcribed together with the hyp-genes in Nostoc PCC 7120. The ORFs upstream the hyp-genes can be found in the same genomic arrangement in other filamentous, nitrogen fixing cyanobacterial strains but are interestingly missing in strains incapable of nitrogen fixation. In this study we have further investigated the function of the ORFs upstream the hyp-genes by studying their transcription pattern after nitrogen depletion in the filamentous, nitrogen fixing strains Nostoc PCC 7120 and N. punctiforme. The transcription pattern were compared to the transcription pattern of hupS and hoxY, encoding the uptake and bidirectional hydrogenase small subunits, nifD, encoding a nitrogenase subunit and hypC and hypF, encoding the maturation process accessory proteins HypC and HypF. All the five ORFs upstream the hyp-genes, in both organisms, were upregulated after nitrogen step down in accordance with the transcription pattern for hupS, nifD, hypC and hypF which support the theory that these genes might be involved in the maturation of the small subunit.

    Place, publisher, year, edition, pages
    London: BioMed Central, 2011
    Keywords
    Nostoc sp.strain PCC 7120, Nostoc punctiforme ATCC29133, hyp, hydrogenase maturation
    National Category
    Biochemistry and Molecular Biology
    Identifiers
    urn:nbn:se:uu:diva-110865 (URN)10.1186/1756-0500-4-186 (DOI)
    Available from: 2009-11-27 Created: 2009-11-27 Last updated: 2017-12-12
  • 8.
    Agervald, Åsa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Baebprasert, Wipawee
    Program of Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok, Thailand.
    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.
    The CyAbrB transcription factor Alr0946 regulates the iron superoxide dismutase in Nostoc sp. strain PCC 7120Manuscript (preprint) (Other academic)
    Abstract [en]

    In the present investigation we analyse the results of induced over-production of the CyAbrB transcription factor Alr0946 in the cyanobacterium Nostoc sp. PCC 7120 with special focus on its effects on FeSOD. With gel based quantitative proteomics the induced over-expression of Alr0946 was shown to influence the abundance of at least 25 proteins. One of the proteins with a significant lower abundance was FeSOD, one of two types of superoxide dismutases in Nostoc sp. PCC 7120. The change in protein abundance was also followed by lower transcript as well as activity levels. Purified Alr0946 from Nostoc sp. PCC 7120 was shown to interact with the promoter region of alr2938, encoding FeSOD, indicating a transcriptional regulation of FeSOD by Alr0946. The Alr0946 over-expression strain showed a bleaching phenotype with lower growth rate and truncated filaments already two days after induction of over-expression. The phenotype was even more pronounced when illumination was increased from 35 to 125 μmol m-2s-1. This is in line with an increased need of FeSOD during a stronger oxidative stress. The results indicate that Alr0946 is involved in regulation of stress responses and that FeSOD has a specific and important function in the oxidative stress tolerance of the multicellular cyanobacterium Nostoc sp. PCC 7120.

  • 9.
    Agervald, Åsa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Baebprasert, Wipawee
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Zhang, Xiaohui
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Incharoensakdi, Aran
    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.
    The CyAbrB transcription factor CalA regulates the iron superoxide dismutase in Nostoc sp. strain PCC 71202010In: Environmental Microbiology, ISSN 1462-2912, E-ISSN 1462-2920, Vol. 12, no 10, p. 2826-2837Article in journal (Refereed)
    Abstract [en]

    P>In the present investigation the results of induced over-production of the CyAbrB transcription factor CalA (Cyanobacterial AbrB-like, annotated as Alr0946) in the cyanobacterium Nostoc sp. PCC 7120 were analysed. The CalA overexpression strain showed a bleaching phenotype with lower growth rate and truncated filaments 2 days after induction of overexpression. The phenotype was even more pronounced when illumination was increased from 35 to 125 mu mol m-2 s-1. Using gel-based quantitative proteomics, the induced overexpression of CalA was shown to downregulate the abundance of FeSOD, one of two types of superoxide dismutases in Nostoc sp. PCC 7120. The change in protein abundance was also accompanied by lower transcript as well as activity levels. Purified recombinant CalA from Nostoc sp. PCC 7120 was shown to interact with the promoter region of alr2938, encoding FeSOD, indicating a transcriptional regulation of FeSOD by CalA. The bleaching phenotype is in line with a decreased tolerance against oxidative stress and indicates that CalA is involved in regulation of cellular responses in which FeSOD has an important and specific function in the filamentous cyanobacterium Nostoc sp. PCC 7120.

  • 10.
    Agervald, Åsa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics. Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Camsund, Daniel
    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.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    CRISPR in the extended hyp-operon of the cyanobacterium Nostoc sp. strain PCC 7120, characteristics and putative function(s)2012In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 37, no 10, p. 8828-8833Article in journal (Refereed)
    Abstract [en]

    The presence of small RNAs (sRNA) and their functions in transcriptional regulation has lately turned into a hot topic. Since cyanobacteria often face changes in the surrounding environment, they need to have a well working system for stress response. Quick adaption is necessary, and an RNA-based regulatory system is thus useful. One example of these sRNAs is CRISPRs. In this work we report the existence of a CRISPR within the hyp-operon (hyp genes encode proteins responsible for the maturation of hydrogenases) of the filamentous cyanobacterium Nostoc sp. strain PCC 7120. We present data concerning its characteristics and putative function(s) and raise the question concerning the importance of this CRISPR array and other CRISPR systems in general. In addition, we discuss the use of the CRISPR system as a potential bacterial genetic defence mechanism to achieve robust, cyanobacterial cultures in large scale, commercial production units.

  • 11.
    Agervald, Åsa
    et al.
    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.
    Holmqvist, Marie
    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.
    Transcription of the extended hyp-operon in Nostoc sp. strain PCC 71202008In: BMC Microbiology, ISSN 1471-2180, E-ISSN 1471-2180, Vol. 8, p. 69-Article in journal (Refereed)
    Abstract [en]

    Background: The maturation of hydrogenases into active enzymes is a complex process and e. g. a correctly assembled active site requires the involvement of at least seven proteins, encoded by hypABCDEF and a hydrogenase specific protease, encoded either by hupW or hoxW. The N2fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain both an uptake and a bidirectional hydrogenase. The present study addresses the presence and expression of hypgenes in Nostoc sp. strain PCC 7120. Results: RTPCRs demonstrated that the six hypgenes together with one ORF may be transcribed as a single operon. Transcriptional start points (TSPs) were identified 280 bp upstream from hypF and 445 bp upstream of hypC, respectively, demonstrating the existence of several transcripts. In addition, five upstream ORFs located in between hupSL, encoding the small and large subunits of the uptake hydrogenase, and the hypoperon, and two downstream ORFs from the hypgenes were shown to be part of the same transcript unit. A third TSP was identified 45 bp upstream of asr0689, the first of five ORFs in this operon. The ORFs are annotated as encoding unknown proteins, with the exception of alr0692 which is identified as a NifUlike protein. Orthologues of the four ORFs asr0689alr0692, with a highly conserved genomic arrangement positioned between hupSL, and the hyp genes are found in several other N2fixing cyanobacteria, but are absent in non N2fixing cyanobacteria with only the bidirectional hydrogenase. Short conserved sequences were found in six intergenic regions of the extended hypoperon, appearing between 11 and 79 times in the genome. Conclusion: This study demonstrated that five ORFs upstream of the hypgene cluster are cotranscribed with the hypgenes, and identified three TSPs in the extended hypgene cluster in Nostoc sp. strain PCC 7120. This may indicate a function related to the assembly of a functional uptake hydrogenase, hypothetically in the assembly of the small subunit of the enzyme.

  • 12.
    Agervald, Åsa
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Zhang, Xiaohui
    Department of Biological Sciences, Purdue University.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Devine, Ellenor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    CalA, a cyanobacterial AbrB protein, interacts with the upstream region of hypC and acts as a repressor of its transcription in the cyanobacterium Nostoc sp. strain PCC 71202010In: Applied and Environmental Microbiology, ISSN 0099-2240, E-ISSN 1098-5336, Vol. 76, no 3, p. 880-890Article in journal (Refereed)
    Abstract [en]

    The filamentous, heterocystous, nitrogen-fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain, depending on growth condition, up to two hydrogenases directly involved in hydrogen metabolism. HypC is one out of at least seven auxiliary gene products required for synthesis of a functional hydrogenase, specifically involved in the maturation of the large subunit. In this study we present a protein, Alr0946, belonging to the transcription regulator family AbrB, which in protein-DNA assays was found to interact with the upstream region of hypC. Transcriptional investigations showed that alr0946 is co-transcribed with the downstream gene alr0947, which encodes a putative protease from the abortive infection superfamily, Abi. Alr0946 was shown to interact specifically not only with the upstream region of hypC but also with its own upstream region, acting as a repressor on both. The bidirectional hydrogenase activity was significant down-regulated when Alr0946 was over-expressed demonstrating a correlation to the transcription factor, either direct or indirect. In silico studies showed that homologues to both Alr0946 and Alr0947 are highly conserved proteins within cyanobacteria with a very similar physical organisation of the corresponding structural genes. Possible functions of the co-transcribed downstream protein Alr0947 are presented. In addition, we present a 3D model of the CyAbrB domain of Alr0946 and putative DNA-binding mechanisms are discussed.

  • 13. Allahverdiyeva, Yagut
    et al.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Holmström, Maija
    Nurmi, Markus
    Lundin, Björn
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Spetea, Cornelia
    Aro, Eva-Mari
    Comparison of the electron transport properties of the psbo1 and psbo2 mutants of Arabidopsis thaliana2009In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1787, no 10, p. 1230-1237Article in journal (Refereed)
    Abstract [en]

    Genome sequence of Arabidopsis thaliana (Arabidopsis) revealed two psbO genes (At5g66570 and At3g50820) which encode two distinct PsbO isoforms: PsbO1 and PsbO2, respectively. To get insights into the function of the PsbO1 and PsbO2 isoforms in Arabidopsis we have performed systematic and comprehensive investigations of the whole photosynthetic electron transfer chain in the T-DNA insertion mutant lines, psbO1 and psbo2. The absence of the PsbO1 isoform and presence of only the PsbO2 isoform in the psbo1 mutant results in (i) malfunction of both the donor and acceptor sides of Photosystem (PS) 11 and (ii) high sensitivity of PSII centers to photodamage, thus implying the importance of the PsbO1 isoform for proper structure and function of PSII. The presence of only the PsbO2 isoform in the PSII centers has consequences not only to the function of PSII but also to the PSI/PSII ratio in thylakoids. These results in modification of the whole electron transfer chain with higher rate of cyclic electron transfer around PSI, faster induction of NPQ and a larger size of the PQ-pool compared to WT, being in line with apparently increased chlororespiration in the psbo1 mutant plants. The presence of only the PsbO1 isoform in the psbo2 mutant did not induce any significant differences in the performance of PSII under standard growth conditions as compared to WT. Nevertheless, under high light illumination, it seems that the presence of also the PsbO2 isoform becomes favourable for efficient repair of the PSII complex.

  • 14. Allahverdiyeva, Yagut
    et al.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Suorsa, Marjaana
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Vass, Imre
    Aro, Eva-Mari
    Insights into the function of PsbR protein in Arabidopsis thaliana2007In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1767, no 6, p. 677-685Article in journal (Refereed)
    Abstract [en]

    The functional state of the Photosystem (PS) II complex in Arabidopsis psbR T-DNA insertion mutant was studied. The DeltaPsbR thylakoids showed about 34% less oxygen evolution than WT, which correlates with the amounts of PSII estimated from Y(D)(ox) radical EPR signal. The increased time constant of the slow phase of flash fluorescence (FF)-relaxation and upshift in the peak position of the main TL-bands, both in the presence and in the absence of DCMU, confirmed that the S(2)Q(A)(-) and S(2)Q(B)(-) charge recombinations were stabilized in DeltaPsbR thylakoids. Furthermore, the higher amount of dark oxidized Cyt-b559 and the increased proportion of fluorescence, which did not decay during the 100s time span of the measurement thus indicating higher amount of Y(D)(+)Q(A)(-) recombination, pointed to the donor side modifications in DeltaPsbR. EPR measurements revealed that S(1)-to-S(2)-transition and S(2)-state multiline signal were not affected by mutation. The fast phase of the FF-relaxation in the absence of DCMU was significantly slowed down with concomitant decrease in the relative amplitude of this phase, indicating a modification in Q(A) to Q(B) electron transfer in DeltaPsbR thylakoids. It is concluded that the lack of the PsbR protein modifies both the donor and the acceptor side of the PSII complex.

  • 15.
    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.

  • 16.
    Anderlund, Magnus F.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Zheng, J.
    Ghiladi, Marten
    Kritikos, Mikael
    Riviere, Eric
    Sun, Licheng
    Girerd, Jean-Jacques
    Åkermark, Björn
    A new, dinuclear high spin manganese(III) complex with bridging phenoxy and methoxy groups. Structure and magnetic properties2006In: Inorganic Chemistry Communications, Vol. 9, no 12, p. 1195-1198Article in journal (Refereed)
  • 17.
    Andersson, Claes-Henrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry.
    Synthesis and IR Spectroelectrochemical Studies of a [60]Fulleropyrrolidine-(tricarbonyl)chromium Complex: Probing C-60 Redox States by IR Spectroscopy2011In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, no 11, p. 1744-1749Article in journal (Refereed)
    Abstract [en]

    The synthesis of a new fulleropyrrolidine-(tricarbonyl)chromium complex: 1-methyl-2-(4-methoxyphenyl)-3,4-[60]fulleropyrrolidine-(tricarbonyl)chromium is described together with its characterization by IR, NMR and cyclic voltammetry. IR spectro-electrochemistry has been used to probe the redox level of the fullerene derivative via the relative position of the vibrational bands of the CO ligands, which are sensitive to the electronic state of the complex. Other strategies to incorporate a tricarbonylchromium moiety to fullerene C60 are also briefly discussed and evaluated.

  • 18. Andersson, Magnus
    et al.
    Malmerberg, Erik
    Westenhoff, Sebastian
    Katona, Gergely
    Cammarata, Marco
    Wohri, Annemarie B.
    Johansson, Linda C.
    Ewald, Friederike
    Eklund, Mattias
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Wulff, Michael
    Davidsson, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Neutze, Richard
    Structural Dynamics of Light-Driven Proton Pumps2009In: Structure, ISSN 0969-2126, E-ISSN 1878-4186, Vol. 17, no 9, p. 1265-1275Article in journal (Refereed)
    Abstract [en]

    Bacteriorhodopsin and proteorhodopsin are simple heptahelical proton pumps containing a retinal chromophore covalently bound to helix G via a protonated Schiff base. Following the absorption of a photon, all-trans retinal is isomerized to a 13-cis conformation, initiating a sequence of conformational changes driving vectorial proton transport. In this study we apply time-resolved wide-angle X-ray scattering to visualize in real time the helical motions associated with proton pumping by bacteriorhodopsin and proteorhodopsin. Our results establish that three conformational states are required to describe their photocycles. Significant motions of the cytoplasmic half of helix F and the extracellular half of helix C are observed prior to the primary proton transfer event, which increase in amplitude following proton transfer. These results both simplify the structural description to emerge from intermediate trapping studies of bacteriorhodopsin and reveal shared dynamical principles for proton pumping.

  • 19. Andersson, Magnus
    et al.
    Vincent, Jonathan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    van der Spoel, David
    Uppsala University, Disciplinary Domain of Science and Technology, Biology, Department of Cell and Molecular Biology.
    Davidsson, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Neutze, Richard
    A proposed time-resolved X-ray scattering approach to track local and global conformational changes in membrane transport proteins2008In: Structure, ISSN 0969-2126, E-ISSN 1878-4186, Vol. 16, no 1, p. 21-28Article in journal (Refereed)
    Abstract [en]

    Time-resolved X-ray scattering has emerged as a powerful technique for studying the rapid structural dynamics of small molecules in solution. Membrane-protein-catalyzed transport processes frequently couple large-scale conformational changes of the transporter with local structural changes perturbing the uptake and release of the transported substrate. Using light-driven halide ion transport catalyzed by halorhodopsin as a model system, we combine molecular dynamics simulations with X-ray scattering calculations to demonstrate how small-molecule time-resolved X-ray scattering can be extended to the study of membrane transport processes. In particular, by introducing strongly scattering atoms to label specific positions within the protein and substrate, the technique of time-resolved wide-angle X-ray scattering can reveal both local and global conformational changes. This approach simultaneously enables the direct visualization of global rearrangements and substrate movement, crucial concepts that underpin the alternating access paradigm for membrane transport proteins.

  • 20. Angermayr, S. Andreas
    et al.
    Hellingwerf, Klaas J.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    de Mattos, M. Joost Teixeira
    Energy biotechnology with cyanobacteria2009In: Current Opinion in Biotechnology, ISSN 0958-1669, E-ISSN 1879-0429, Vol. 20, no 3, p. 257-263Article, review/survey (Refereed)
    Abstract [en]

    The world's future energy demand calls for a sustainable alternative for the use of fossil fuels, to restrict further global warming. Harvesting solar energy via photosynthesis is one of Nature's remarkable achievements. Existing technologies exploit this process for energy 'production' via processing of, for example, part of plant biomass into ethanol, and of algal biomass into biodiesel. Fortifying photosynthetic organisms with the ability to produce biofuels directly would bypass the need to synthesize all the complex chemicals of 'biomass'. A promising way to achieve this is to redirect cyanobacterial intermediary metabolism by channeling (Calvin cycle) intermediates into fermentative metabolic pathways. This review describes this approach via the biosynthesis of fermentation end products, like alcohols and hydrogen, driven by solar energy, from water (and CO2).

  • 21. Antal, Taras
    et al.
    Oliveira, Paulo
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lindblad, Peter
    The bidirectional hydrogenase in the cyanobacterium Synechocystis sp. strain PCC 68032006In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 31, no 11, p. 1439-1444Article in journal (Refereed)
  • 22.
    Arkhypchuk, Anna I.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Reductive Diphosphene Formation From W(CO)5-Coordinated Dichlorophosphanes2011In: Phosphorus Sulfur and Silicon and the Related Elements, ISSN 1042-6507, E-ISSN 1563-5325, Vol. 186, no 4, p. 664-665Article in journal (Refereed)
    Abstract [en]

    A bis-[W(CO)(5)]-coordinated (Bu-t)(2)diphosphene was prepared from the corresponding [W(CO)(5)]-(BuPCl2)-Bu-t by treatment with LiAlH4.

  • 23.
    Astuti, Yeni
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Topoglidis, Emmanuel
    Cass, G
    Durrant, James R.
    Direct spectroelectrochemistry of peroxidases immobilised on mesoporous metal oxide electrodes: Towards reagentless hydrogen peroxide sensing2009In: Analytica Chimica Acta, ISSN 0003-2670, E-ISSN 1873-4324, Vol. 648, no 1, p. 2-6Article in journal (Refereed)
    Abstract [en]

    In this paper, we employ two peroxidases (horseradish peroxidase, HRP and cytochrome c peroxidase, CcP) to demonstrate their ability to retain their redox and biological functions after their immobilisation on mesoporous TiO2 and SnO2 electrodes. We will also demonstrate the use of HRP immobilised on the metal oxide electrodes for the development of reagentless optical and electrochemical biosensors for the detection of hydrogen peroxide (H2O2) with low detection limit of 0.04 and 1 mu M, respectively. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

  • 24.
    Baebprasert, Wipawee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Jantaro, Saowarath
    Khetkorn, Wanthanee
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Incharoensakdi, Aran
    Increased H(2) production in the cyanobacterium Synechocystis sp strain PCC 6803 by redirecting the electron supply via genetic engineering of the nitrate assimilation pathway2011In: Metabolic engineering, ISSN 1096-7176, E-ISSN 1096-7184, Vol. 13, no 5, p. 610-616Article in journal (Refereed)
    Abstract [en]

    The unicellular cyanobacterium Synechocystis sp. strain PCC 6803 contains a single bidirectional NiFe-Hox-hydrogenase, which evolves hydrogen under certain environmental conditions. The nitrate assimilation pathway is a potential competing pathway that may reduce the electron flow to the hydrogenase and thereby limit hydrogen production. To improve H(2) production, the nitrate assimilation pathway was disrupted by genetic engineering to redirect the electron flow towards the Hox-hydrogenase. Mutant strains disrupted in either nitrate reductase (Delta narB) or nitrite reductase (Delta nirA) or both nitrate reductase and nitrite reductase (Delta narB:Delta nirA) were constructed and tested for their ability to produce hydrogen. H(2) production and Hox-hydrogenase activities in all the mutant strains were higher than those in wild-type. Highest H(2) production was observed in the Delta narB:Delta nirA strain. Small changes were observed for Hox-hydrogenase enzyme activities and only minor changes in transcript levels of hoxH and hoxY were not correlated with H(2) production. The results suggest that the high rate of H(2) production observed in the Delta narB:Delta nirA strain of the cyanobacterium Synechocystis sp. strain PCC 6803 is the result of redirecting the electron supply from the nitrate assimilation pathway, through genetic engineering, towards the Hox-hydrogenase.

  • 25.
    Baebprasert, Wipawee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Karnchanatat, Aphichart
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Incharoensakdi, Aran
    Na(+)-stimulated nitrate uptake with increased activity under osmotic upshift in Synechocystis sp strain PCC 68032011In: World Journal of Microbiology & Biotechnology, ISSN 0959-3993, E-ISSN 1573-0972, Vol. 27, no 10, p. 2467-2473Article in journal (Refereed)
    Abstract [en]

    In the non-diazotrophic cyanobacterium Synechocystis sp. strain PCC 6803, an osmolality of 30 and 40 mosmol/kg sorbitol and NaCl resulted in 3.5- and 4.5-fold increase of nitrate uptake, respectively. The NaCl-stimulated uptake was abolished by treatment with chloramphenicol. At 25 mosmol/kg or higher, NaCl induced higher nitrate uptake than sorbitol suggesting an ionic effect of Na(+). The nitrate uptake in Synechocystis showed K (s) and V (max) values of 46 mu M and 1.37 mu mol/min/mg Chl, respectively. Mutants disrupted in nitrate and nitrite reductase exhibited a decreased nitrate uptake. Ammonium, chlorate, and dl-glyceraldehyde caused a reduction of nitrate uptake. Dark treatment caused a drastic reduction of uptake by 70% suggesting an energy-dependent system. Nitrate transport was sensitive to various metabolic inhibitors including those dissipating proton gradients and membrane potential. The results suggest that nitrate uptake in Synechocystis is stimulated by Na(+) ions and requires energy provided by the functioning electron transport chain.

  • 26. Baebprasert, Wipawee
    et al.
    Lindblad, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Incharoensakdi, Aran
    Response of H-2 production and Hox-hydrogenase activity to external factors in the unicellular cyanobacterium Synechocystis sp strain PCC 68032010In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 35, no 13, p. 6611-6616Article in journal (Refereed)
    Abstract [en]

    The effects of external factors on both H-2 production and bidirectional Hox-hydrogenase activity were examined in the non-N-2-fixing cyanobacterium Synechocystis PCC 6803. Exogenous glucose and increased osmolality both enhanced H-2 production with optimal production observed at 0.4% and 20 mosmol kg(-1), respectively. Anaerobic condition for 24 h induced significant higher H(2)ase activity with cells in BC11(0) showing highest activities. Increasing the pH resulted in an increased Hox-hydrogenase activity with an optimum at pH 7.5. The Hox-hydrogenase activity gradually increased with increasing temperature from 30 degrees C to 60 degrees C with the highest activity observed at 70 degrees C. A low concentration at 100 mu M of either DTT or beta-mercaptoethanol resulted in a minor stimulation of H-2 production. beta-Mercaptoethanol added to nitrogen- and sulfur-deprived cells stimulated H-2 production significantly. The highest Hox-hydrogenase activity was observed in cells in BG11(0)-S-deprived condition and 750 mu M beta-mercaptoethanol measured at a temperature of 70 degrees C; 14.32 mu mol H-2 mg chl alpha(-1) min(-1).

  • 27. Ballout, Fouad
    et al.
    Krassen, Henning
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Kopf, Ilona
    Ataka, Kenichi
    Bruendermann, Erik
    Heberle, Joachim
    Havenith, Martina
    Scanning near-field IR microscopy of proteins in lipid bilayers2011In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 13, no 48, p. 21432-21436Article in journal (Refereed)
    Abstract [en]

    We use infrared near-field microscopy to chemically map the morphology of biological matrices. The investigated sample is built up from surface-tethered membrane proteins (cytochrome c oxidase) reconstituted in a lipid bilayer. We have carried out infrared near-field measurements in the frequency range between 1600 and 1800 cm(-1). By simultaneously recording the topography and chemical fingerprint of the protein-tethered lipid bilayer with a lateral resolution of 80 nm x 80 nm, we were able to probe locally the chemical signature of this membrane and to provide a local map of its surface morphology.

  • 28.
    Becker, Hans-Christian
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Kilsa, Kristine
    Size- and solvent-dependent kinetics for cis-trans isomerization in donor-acceptor systems2009In: Spectrochimica Acta Part A - Molecular and Biomolecular Spectroscopy, ISSN 1386-1425, E-ISSN 1873-3557, Vol. 72, no 5, p. 1014-1019Article in journal (Refereed)
    Abstract [en]

    We have investigated, using time-resolved and steady-state optical spectroscopy, the cis-trans isomerization dynamics in a series of charge transfer. donor-acceptor compounds. The number of donor (dithiafulvene) and acceptor (p-nitrophenyl) moieties as well as their spatial arrangement around a central ethynylethene core has been varied in a systematic way, All compounds in the series are weakly fluorescent. We show that the fluorescence spectrum red-shifts within a few picoseconds, a shift which occurs concurrently with a blue-shift of the transient absorption spectrum. The kinetics following the initial relaxation are in all cases multi-exponential, and the time constants correlate with molecular size and solvent viscosity. We interpret the data as a result of conformational change where the conjugation through the central double bond is broken upon excitation into the charge-transfer transition, and the time for rotation around this bond is dependent on the molecular interactions between solute and solvent. (C) 2009 Elsevier B.V. All Fights reserved.

  • 29. Beckmann, K.
    et al.
    Uchtenhagen, Hannes
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Anderlund, Magnus F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Messinger, J.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Kurz, P.
    Formation of stoichiometrically O-18-labelled oxygen from the oxidation of O-18-enriched water mediated by a dinuclear manganese complex: a mass spectrometry and EPR study2008In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 1, no 6, p. 668-676Article 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 O-2, (H2O)-O-18 isotope-labelling experiments coupled with membrane inlet mass spectrometry (MIMS) were carried out. We discovered that during the reaction of oxone with [Mn-2(OAc)(2)(bpmp)](+) (1), stoichiometrically labelled oxygen (O-18(2)) 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 O-18(2) 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.

  • 30.
    Berggren, G.
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Photochemistry and Molecular Science, Molecular Biomimetics. Avdelningen för molekylär biomimetik.
    Anderlund, M.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Photochemistry and Molecular Science, Molecular Biomimetics. Avdelningen för molekylär biomimetik.
    Magnuson, A.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical Chemistry. Department of Photochemistry and Molecular Science, Molecular Biomimetics. Avdelningen för molekylär biomimetik.
    Åkermark, B.
    Eriksson, L.
    Sodium [1,2-bis(2-methyl-2-oxopropanamido)-benzene](tetrahydrofuran) manganese(III) methanol solvate2005In: Acta Crystallographica Section E-Structure Reports Online, Vol. 61, p. M1169-Article in journal (Refereed)
  • 31.
    Berggren, Gustav
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Mimicking Nature – Synthesis and Characterisation of Manganese Complexes of Relevance to Artificial Photosynthesis2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The development of efficient catalyst for water oxidation is of paramount importance to artificial photosynthesis, but before this can be achieved a deeper understanding of this reaction is essential. In nature this reaction occurs in a tetranuclear Mn-cluster which serves as the work-horse of oxygenic photosynthesis. This thesis summarises my efforts at developing molecular systems capable of mimicking this complex employing a biomimetic approach.

    Three different approaches towards this goal are described here-in. The first section describes a screening study, in which a number of manganese complexes were tested to see whether or not they were capable of catalysing the formation of dioxygen when treated with different oxidants (Papers I). For those reactions in which dioxygen formation was observed the reactions were repeated in labelled water and the incorporation of labelled O-atoms was studied by mass spectrometry. This allowed us to determine to what extent water was the source of the evolved dioxygen (Papers II-III).

    In Chapter three a reported catalyst and a derivative thereof is studied in depth. The influence of changes to the ligand on the oxygen–oxygen bond forming reaction could unfortunately not be reliably addressed, because of the instability of the complexes under “catalytic” conditions. Nevertheless, the study allowed us to revise the “carboxylate shift”-mechanism suggested in the literature (Papers IV-V).

    Chapter four describes the continuation of my work on ligands featuring the carboxylate ligand motif first introduced in Chapter three. In this study ligands containing multiple binding pockets were designed and synthesised (Paper VI).

    A better understanding of the mechanism in the natural water oxidising enzyme will facilitate the design of biomimetic complexes, this is discussed in Chapter five. In this work model complexes (Paper VII) are used to study the mechanism by which natures own water oxidising catalyst performs this reaction.

    List of papers
    1. Formation of stoichiometrically O-18-labelled oxygen from the oxidation of O-18-enriched water mediated by a dinuclear manganese complex: a mass spectrometry and EPR study
    Open this publication in new window or tab >>Formation of stoichiometrically O-18-labelled oxygen from the oxidation of O-18-enriched water mediated by a dinuclear manganese complex: a mass spectrometry and EPR study
    Show others...
    2008 (English)In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 1, no 6, p. 668-676Article in journal (Refereed) Published
    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 O-2, (H2O)-O-18 isotope-labelling experiments coupled with membrane inlet mass spectrometry (MIMS) were carried out. We discovered that during the reaction of oxone with [Mn-2(OAc)(2)(bpmp)](+) (1), stoichiometrically labelled oxygen (O-18(2)) 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 O-18(2) 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.

    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-108518 (URN)10.1039/b811806j (DOI)000263888600006 ()1754-5692 (ISBN)
    Available from: 2009-09-21 Created: 2009-09-21 Last updated: 2017-12-13
    2. Sodium [1,2-bis(2-methyl-2-oxopropanamido)-benzene](tetrahydrofuran) manganese(III) methanol solvate
    Open this publication in new window or tab >>Sodium [1,2-bis(2-methyl-2-oxopropanamido)-benzene](tetrahydrofuran) manganese(III) methanol solvate
    Show others...
    2005 (English)In: Acta Crystallographica Section E-Structure Reports Online, Vol. 61, p. M1169-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-75924 (URN)
    Available from: 2006-02-24 Created: 2006-02-24 Last updated: 2011-01-11
    3. Two tetranuclear Mn-complexes as biomimetic models of the oxygen evolving complex in Photosystem II. A synthesis, characterisation and reactivity study
    Open this publication in new window or tab >>Two tetranuclear Mn-complexes as biomimetic models of the oxygen evolving complex in Photosystem II. A synthesis, characterisation and reactivity study
    Show others...
    2009 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 45, p. 10044-10054Article in journal (Refereed) Published
    National Category
    Inorganic Chemistry
    Identifiers
    urn:nbn:se:uu:diva-108451 (URN)10.1039/b906175d (DOI)
    Available from: 2009-09-21 Created: 2009-09-18 Last updated: 2017-12-13
    4. Mechanistic Studies on the Water-Oxidizing Reaction of Homogeneous Manganese-Based Catalysts: Isolation and Characterization of a Suggested Catalytic Intermediate
    Open this publication in new window or tab >>Mechanistic Studies on the Water-Oxidizing Reaction of Homogeneous Manganese-Based Catalysts: Isolation and Characterization of a Suggested Catalytic Intermediate
    Show others...
    2011 (English)In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, no 8, p. 3425-3430Article in journal (Refereed) Published
    Abstract [en]

    The synthesis, isolation, and characterization of two high-valent manganese dimers with isomeric ligands are reported. The complexes are synthesized and crystallized from solutions of low-valent precursors exposed to tert-butyl hydroperoxide. The crystal structures display centrosymmetric complexesconsisting of Mn2 IV,IV(μ-O)2 cores, with one ligand coordinating to each manganese. The ligands coordinate with the diaminoethane backbone, the carboxylate, and one of the two pyridines, while the second pyridine is noncoordinating. The activity of these complexes, under water oxidation conditions, is discussed in light of a proposed mechanism for water oxidation, in which this type of complexes have been suggested as a key intermediate.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-108524 (URN)10.1021/ic102336a (DOI)000290457700034 ()21428420 (PubMedID)
    Available from: 2009-09-21 Created: 2009-09-21 Last updated: 2017-12-13
    5. Synthesis and characterisation of low valent Mn-complexes as models for Mn-catalases
    Open this publication in new window or tab >>Synthesis and characterisation of low valent Mn-complexes as models for Mn-catalases
    Show others...
    2010 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 45, p. 11035-11044Article in journal (Refereed) Published
    Abstract [en]

    In this work we report the synthesis of two novel manganese complexes, [L1(3)Mn(6)(II)](ClO4)(6) (1 center dot(ClO4)(6)) and [L2Mn(2)(II)(mu-OAc)(mu-Cl)](ClO4)(2) (2 center dot(ClO4)(2)), where L1(2-) is the 2,2'-(1,3-phenylenebis(methylene))bis-((2-(bis(pyridin-2-ylmethyl)amino)ethyl)azanediyl)diacetic acid anion and L2 is N1,N1'-(1,3-phenylenebis(methylene))bis(N2,N2'-bis(pyridin-2-ylmethyl)ethane-1,2-diamine). The ligands Na(2)L1 and L2 are built on the same backbone, L2 only contains nitrogen donors, while two carboxylate arms have been introduced in Na(2)L1. The two complexes have been characterized by single-crystal X-ray diffraction, magnetic susceptibility, EPR spectroscopy, and electrochemistry. X-Ray crystallography revealed that 1 is a manganese(II) hexamer and 2 is a manganese(II) dimer featuring an unprecedented mono-mu-acetato, mono-mu-chlorido bridging motif. The ability of the complexes to catalyse H2O2 disproportionation, thereby acting as models for manganese catalases, has been investigated and compared to the activity of two other related manganese complexes. The introduction of carboxylate donors in the ligands, leading to increased denticity, resulted in a drop in H2O2 disproportionation activity.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-108525 (URN)10.1039/c0dt00165a (DOI)000284066100028 ()
    Available from: 2009-09-21 Created: 2009-09-21 Last updated: 2017-12-13
    6. Oxygen evolving reactions catalysed by synthetic manganese complexes: A systematic screening
    Open this publication in new window or tab >>Oxygen evolving reactions catalysed by synthetic manganese complexes: A systematic screening
    2007 (English)In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, no 38, p. 4258-4261Article in journal (Refereed) Published
    Abstract [en]

    A set of six multinuclear manganese complexes was screened for the ability to catalyse reactions yielding O(2) under coherent experimental conditions; we identify a much larger number of manganese compounds than previously known that catalyse oxygen formation.

    National Category
    Chemical Sciences
    Identifiers
    urn:nbn:se:uu:diva-11551 (URN)10.1039/b710761g (DOI)000249705100004 ()17893814 (PubMedID)
    Available from: 2007-09-27 Created: 2007-09-27 Last updated: 2017-12-11
    7. Oxygen Evolving Reactions by Synthetic Manganese Complexes
    Open this publication in new window or tab >>Oxygen Evolving Reactions by Synthetic Manganese Complexes
    Show others...
    2008 (English)In: Photosynthesis. Energy from the Sun: 14th International Congress on Photosynthesis, Springer, Netherlands , 2008Chapter in book (Other (popular science, discussion, etc.))
    Place, publisher, year, edition, pages
    Springer, Netherlands, 2008
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:uu:diva-108452 (URN)978-1-4020-6707-5 (ISBN)
    Available from: 2009-09-21 Created: 2009-09-18 Last updated: 2015-04-24
  • 32.
    Berggren, Gustav
    et al.
    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
    Anderlund, Magnus F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Synthesis, Characterization and Reactivity Study of a New Penta-Coordinated Mn(II) Complex2009In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 36, no 1, p. 9-24Article in journal (Refereed)
    Abstract [en]

    A penta-coordinated Mn(II) compound [dqpMnCl(2)] (1) (dqp = 2,6-di-(8-quinoline-yl)-pyridine) has been synthesized and its X-ray crystallographic structure is reported here. Magnetic susceptibility measurements confirmed a high-spin Mn(II) (S = 5/2) center in 1. The X-band EPR spectrum of 1 in dimethylformamide solution exhibits widely distributed transitions in the spectral range from 0 to 700 mT with particularly well-resolved hyperfine lines due to the Mn-55 (I = 5/2) nucleus. The abundance of highly resolved transition lines in the spectrum facilitated the electron paramagnetic resonance spectral simulation which revealed large zero-field splitting and g-anisotropies. When dissolved, 1 exists in equilibrium with a hexa-coordinated species, the latter probably resulting from disassociation of one chlorido-ligand allowing ligation of two solvent molecules. The redox behavior of 1 was studied and was compared to that of a structural analog for which water oxidation in the presence of a chemical oxidant has been shown. The results from water oxidation trials of 1 are discussed.

  • 33.
    Berggren, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Eriksson, Lars
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Anderlund, Magnus F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Synthesis and characterisation of low valent Mn-complexes as models for Mn-catalases2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 45, p. 11035-11044Article in journal (Refereed)
    Abstract [en]

    In this work we report the synthesis of two novel manganese complexes, [L1(3)Mn(6)(II)](ClO4)(6) (1 center dot(ClO4)(6)) and [L2Mn(2)(II)(mu-OAc)(mu-Cl)](ClO4)(2) (2 center dot(ClO4)(2)), where L1(2-) is the 2,2'-(1,3-phenylenebis(methylene))bis-((2-(bis(pyridin-2-ylmethyl)amino)ethyl)azanediyl)diacetic acid anion and L2 is N1,N1'-(1,3-phenylenebis(methylene))bis(N2,N2'-bis(pyridin-2-ylmethyl)ethane-1,2-diamine). The ligands Na(2)L1 and L2 are built on the same backbone, L2 only contains nitrogen donors, while two carboxylate arms have been introduced in Na(2)L1. The two complexes have been characterized by single-crystal X-ray diffraction, magnetic susceptibility, EPR spectroscopy, and electrochemistry. X-Ray crystallography revealed that 1 is a manganese(II) hexamer and 2 is a manganese(II) dimer featuring an unprecedented mono-mu-acetato, mono-mu-chlorido bridging motif. The ability of the complexes to catalyse H2O2 disproportionation, thereby acting as models for manganese catalases, has been investigated and compared to the activity of two other related manganese complexes. The introduction of carboxylate donors in the ligands, leading to increased denticity, resulted in a drop in H2O2 disproportionation activity.

  • 34.
    Berggren, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Kaynak, F. B.
    Anderlund, Magnus F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Eriksson, L.
    Åkermark, B.
    Tetraethylammonium [12,12-diethyl-2,2,9,9-tetramethyl-1,4,7,10-tetraza-5,6-benzotridecane-3 ,8,11,13-tetraone(4-)]oxidomanganate(V)2007In: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 63, no 11, p. M2672-M2673Article in journal (Refereed)
    Abstract [en]

    The Mn-V complex in the title compound, (C8H20N)[ Mn(C21H26N4O4)O], is interesting as it has been suggested that Mn-V oxospecies are intermediates both in epoxidation of alkenes and in water oxidation in PSII, i.e. photosystem II, the protein found in oxygenic photosynthetic organisms, which uses light to split water into O-2, protons and electrons. The Mn atom has a square-pyramidal coordination of four N atoms with an apical O atom. The four N atoms coordinating to Mn [Mn-N = 1.872 (2)-1.882 (2) angstrom] form a plane within 0.03 (3) angstrom from which the Mn ion is displaced by 0.582 (2) angstrom.

  • 35.
    Berggren, Gustav
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Eriksson, Lars
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Anderlund, Magnus F.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Mechanistic Studies on the Water-Oxidizing Reaction of Homogeneous Manganese-Based Catalysts: Isolation and Characterization of a Suggested Catalytic Intermediate2011In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 50, no 8, p. 3425-3430Article in journal (Refereed)
    Abstract [en]

    The synthesis, isolation, and characterization of two high-valent manganese dimers with isomeric ligands are reported. The complexes are synthesized and crystallized from solutions of low-valent precursors exposed to tert-butyl hydroperoxide. The crystal structures display centrosymmetric complexesconsisting of Mn2 IV,IV(μ-O)2 cores, with one ligand coordinating to each manganese. The ligands coordinate with the diaminoethane backbone, the carboxylate, and one of the two pyridines, while the second pyridine is noncoordinating. The activity of these complexes, under water oxidation conditions, is discussed in light of a proposed mechanism for water oxidation, in which this type of complexes have been suggested as a key intermediate.

  • 36.
    Beyler, Maryline
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Ezzaher, Salah
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Karnahl, Michael
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Santoni, Marie-Pierre
    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 Photochemistry and Molecular Science, Chemical Physics.
    Ott, Sascha
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Pentacoordinate iron complexes as functional models of the distal iron in [FeFe] hydrogenases2011In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 47, no 42, p. 11662-11664Article in journal (Refereed)
    Abstract [en]

    Mononuclear pentacoordinate iron complexes with a free coordination site were prepared as mimics of the distal Fe (Fe(d)) in the active site of [FeFe] hydrogenases. The complexes catalyze the electrochemical reduction of protons at mild overpotential.

  • 37. Boixel, Julien
    et al.
    Fortage, Jerome
    Blart, Errol
    Pellegrin, Yann
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Becker, Hans-Christian
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Odobel, Fabrice
    Extension of the charge separated-state lifetime by supramolecular association of a tetrathiafulvalene electron donor to a zinc/gold bisporphyrin2010In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 39, no 6, p. 1450-1452Article in journal (Refereed)
    Abstract [en]

    Supramolecular triads were prepared by self-assembly of 4'-pyridyl-2-tetrathiafulvalene axially bound on ZnP-spacer-AuP+ dyads; the lifetime of the charge separated state (+TTF-ZnP-Spacer-AuP center dot) formed upon light excitation of the triad is greatly increased with respect to that found in the parent dyad.

  • 38.
    Borg, O. Anders
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Karlsson, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Isomäki-Krondahl, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Davidsson, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Lunell, Sten
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
    Predissociation of Chlorobenzene, beyond the pseudo-diatomic model2008In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 456, no 4-6, p. 123-126Article in journal (Refereed)
    Abstract [en]

    Dissociation of chlorobenzene via the lowest singlet excited state has been investigated by means of pump-probe femtosecond spectroscopy and spin-orbit corrected ab initio quantum chemistry. We have found that the so far accepted model with a (1)pi pi* -> (3)pi/n sigma* reaction mechanism has to be amended. We suggest that the mechanism goes via a transition from (1)pi pi* to a pi sigma* state that is to 90% a singlet. Further, three nuclear degrees of freedom required to describe the dissociation have been defined.

  • 39.
    Borg, O Anders
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Department of Physics and Materials Science, Chemical Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Avdelningen för kvantkemi.
    Liu, Ya-Jun
    Persson, Petter
    Lunell, Sten
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Quantum Chemistry. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Department of Physics and Materials Science, Chemical Physics. Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Physical and Analytical Chemistry. Avdelningen för kvantkemi.
    Karlsson, Daniel
    Department of Photochemistry and Molecular Science. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Department of Physics and Materials Science, Chemical Physics.
    Kadi, Malin
    Davidsson, Jan
    Department of Photochemistry and Molecular Science. Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry. Department of Physics and Materials Science, Chemical Physics.
    Photochemistry of bromofluorobenzenes.2006In: J Phys Chem A Mol Spectrosc Kinet Environ Gen Theory, ISSN 1089-5639, Vol. 110, no 22, p. 7045-56Article in journal (Refereed)
  • 40.
    Borgström, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry. Fysikalisk kemi.
    Ott, Sascha
    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.
    Bergquist, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry. Analytisk kemi.
    Hammarström, Leif
    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.
    Photoinduced energy transfer coupled to charge separation in a Ru(II)-Ru(II)-acceptor triad.2006In: Inorganic Chemistry, ISSN 0020-1669, E-ISSN 1520-510X, Vol. 45, no 12, p. 4820-4829Article in journal (Refereed)
  • 41.
    Borgström, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Shaikh, Nizamuddin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Johansson, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical Chemistry.
    Anderlund, Magnus
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Åkerman, Björn
    Magnusson, Ann
    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.
    Light induced manganese oxidation and long-lived charge separation in a Mn2II,II-RuII(bpy)3-acceptor triad2005In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, no 49, p. 17504-17515Article in journal (Refereed)
    Abstract [en]

    The photoinduced electron-transfer reactions in a Mn2II,II-RuII-NDI triad (1) ([Mn2(bpmp)(OAc)2]+, bpmp = 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methylphenolate and OAc = acetate, RuII = tris-bipyridine ruthenium(II), and NDI = naphthalenediimide) have been studied by time-resolved optical and EPR spectroscopy. Complex 1 is the first synthetically linked electron donor-sensitizer-acceptor triad in which a manganese complex plays the role of the donor. EPR spectroscopy was used to directly demonstrate the light induced formation of both products: the oxidized manganese dimer complex (Mn2II,III) and the reduced naphthalenediimide (NDI*-) acceptor moieties, while optical spectroscopy was used to follow the kinetic evolution of the [Ru(bpy)3]2+ intermediate states and the NDI*- radical in a wide temperature range. The average lifetime of the NDI*- radical is ca. 600 micros at room temperature, which is at least 2 orders of magnitude longer than that for previously reported triads based on a [Ru(bpy)3]2+ photosensitizer. At 140 K, this intramolecular recombination was dramatically slowed, displaying a lifetime of 0.1-1 s, which is comparable to many of the naturally occurring charge-separated states in photosynthetic reaction centra. It was found that the long recombination lifetime could be explained by an unusually large reorganization energy (lambda approximately 2.0 eV), due to a large inner reorganization of the manganese complex. This makes the recombination reaction strongly activated despite the large driving force (Delta-G degrees = 1.07 eV). Thus, the intrinsic properties of the manganese complex are favorable for creating a long-lived charge separation in the "Marcus normal region" also when the charge separated state energy is high.

  • 42.
    Camsund, Daniel
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Devine, Ellenor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Holmqvist, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    Peter, Yohanoun
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    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.
    A HupS-GFP fusion protein demonstrates a heterocyst specific localisation of the uptake hydrogenase in the cyanobacterium Nostoc punctiformeIn: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968Article in journal (Refereed)
  • 43.
    Camsund, Daniel
    et al.
    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, Microbial Chemistry.
    Devine, Ellenor
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Holmqvist, Marie
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Yohanoun, Peter
    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.
    Stensjö, Karin
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Microbial Chemistry.
    A HupS-GFP fusion protein demonstrates a heterocyst-specific localization of the uptake hydrogenase in Nostoc punctiforme2011In: FEMS Microbiology Letters, ISSN 0378-1097, E-ISSN 1574-6968, Vol. 316, no 2, p. 152-159Article in journal (Refereed)
    Abstract [en]

    All diazotrophic filamentous cyanobacteria contain an uptake hydrogenase that is involved in the reoxidation of H-2 produced during N-2-fixation. In Nostoc punctiforme ATCC 29133, N-2-fixation takes place in the microaerobic heterocysts, catalysed by a nitrogenase. Although the function of the uptake hydrogenase may be closely connected to that of nitrogenase, the localization in cyanobacteria has been under debate. Moreover, the subcellular localization is not understood. To investigate the cellular and subcellular localization of the uptake hydrogenase in N. punctiforme, a reporter construct consisting of the green fluorescent protein (GFP) translationally fused to HupS, within the complete hupSL operon, was constructed and transferred into N. punctiforme on a self-replicative vector by electroporation. Expression of the complete HupS-GFP fusion protein was confirmed by Western blotting using GFP antibodies. The N. punctiforme culture expressing HupS-GFP was examined using laser scanning confocal microscopy, and fluorescence was exclusively detected in the heterocysts. Furthermore, the fluorescence in mature heterocysts was localized to several small or fewer large clusters, which indicates a specificity of the subcellular localization of the uptake hydrogenase.

  • 44.
    Camsund, Daniel
    et al.
    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.
    Jaramillo, Alfonso
    Genetically engineered light sensors for control of bacterial gene expression2011In: Biotechnology Journal, ISSN 1860-6768, E-ISSN 1860-7314, Vol. 6, no 7, p. 826-836Article, review/survey (Refereed)
    Abstract [en]

    Light of different wavelengths can serve as a transient, noninvasive means of regulating gene expression for biotechnological purposes. Implementation of advanced gene regulatory circuits will require orthogonal transcriptional systems that can be simultaneously controlled and that can produce several different control states. Fully genetically encoded light sensors take advantage of the favorable characteristics of light, do not need the supplementation of any chemical inducers or co-factors, and have been demonstrated to control gene expression in Escherichia coli. Herein, we review engineered light-sensor systems with potential for in vivo regulation of gene expression in bacteria, and highlight different means of extending the range of available light input and transcriptional output signals. Furthermore, we discuss advances in multiplexing different light sensors for achieving multichromatic control of gene expression and indicate developments that could facilitate the construction of efficient systems for light-regulated, multistate control of gene expression.

  • 45.
    Cappel, Ute B.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Smeigh, Amanda L.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Chemical Physics.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Physical Chemistry.
    Characterization of the Interface Properties and Processes in Solid State Dye-Sensitized Solar Cells Employing a Perylene Sensitizer2011In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 115, no 10, p. 4345-4358Article in journal (Refereed)
    Abstract [en]

    We recently reported on a perylene sensitizer, ID176, which performs much better in solid state dye-sensitized solar cells than in those using liquid electrolytes with iodide/tri-iodide as the redox couple (J. Phys. Chem. C2009, 113, 14595-14597). Here, we present a characterization of the sensitizer and of the TiO2/dye interface by UV-visible absorption and fluorescence spectroscopy, spectroelectrochemistry, photoelectron spectroscopy, electroabsorption spectroscopy, photoinduced absorption spectroscopy, and femtosecond transient absorption measurements. We report that the absorption spectrum of the sensitizer is red-shifted by addition of lithium ions to the surface due to a downward shift of the excited state level of the sensitizer, which is of the same order of magnitude as the downward shift of the titanium dioxide conduction band edge. Results from photoelectron spectroscopy and electrochemistry suggest that the excited state is largely located below the conduction band edge of TiO2 but that there are states in the band gap of TiO2 which might be available for photoinduced electron injection. The sensitizer was able to efficiently inject into TiO2, when a lithium salt was present on the surface, while injection was much less effective in the absence of lithium ions or in the presence of solvent. In the presence of the hole conductor 2,2-,7,7-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9-spirobifluorene (spiro-MeOTAD) and LiTFSI, charge separation was monitored by the emergence of a Stark shift of the dye in transient absorption spectra, and both injection and regeneration appear to be completed within 1 ps. Regeneration by spiro-MeOTAD is therefore several orders of magnitude faster than regeneration by iodide, and ID176 can even be photoreduced by spiro-MeOTAD.

  • 46.
    Cardona, Tanai
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    The Heterocysts of Nostoc punctiforme: From Proteomics to Energy Transfer2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The aim of this thesis is to provide a thorough characterization of the photosynthetic machinery from the heterocysts of Nostoc punctiforme strain ATCC 29133. In this thesis I describe the protocols I have optimized for the isolation of thylakoids from vegetative cells, the purification of heterocysts and the isolation of thylakoids from the purified heterocysts. The composition of the thylakoid membranes was studied by two dimensional electrophoresis and mass-spectrometry. Further insight into the functionality of the photosynthetic complexes was obtained by EPR, electron transport measurements through Photosystem II (PSII), and fluorescence spectroscopy. The proteome of the heterocysts thylakoids compared to that of the vegetative cell was found to be dominated by Photosystem I (PSI) and ATP-synthase complexes, both essential for keeping high nitrogenase activities. Surprisingly, we found a significant amount of assembled monomeric PSII complexes in the heterocysts thylakoid membranes. We measured in vitro light-driven electron transfer from PSII in heterocysts using an artificial electron donor, suggesting that under certain circumstances heterocysts might activate PSII. Parallel to my main research I also worked in a collaboration to elucidate the total proteome of Nostoc sp. strain 7120 and Nostoc punctiforme using quantitative shotgun proteomics. Several hundred proteins were quantified for both species. It was possible to trace the detailed changes that occurred in the energy and nitrogen metabolism of a heterocyst after differentiation. Moreover, the presence of PSII proteins identified in our membrane proteome was also confirmed and extended. Lastly, I studied how the heterocysts are capable of responding to variations in light quality as compared to vegetative cells. Using 77 K fluorescence spectroscopy on heterocysts and vegetative cells previously illuminated with light at specific wavelengths, I was able to demonstrate that heterocysts still possess a possibly modified but functional antenna system, capable of harvesting light and transferring energy preferentially to PSI. The characterization of the membrane and total proteome permitted to draw a more comprehensive and integrated picture of the interplay between the distinct metabolic processes that are carried out in each cell type at the same time; from oxygenic photosynthesis and carbon fixation in the vegetative cells to the anoxygenic cyclic photophosphorylation essential to power nitrogen assimilation in the heterocysts.

    List of papers
    1. Isolation and characterization of thylakoid membranes from the filamentous cyanobacterium Nostoc punctiforme
    Open this publication in new window or tab >>Isolation and characterization of thylakoid membranes from the filamentous cyanobacterium Nostoc punctiforme
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    2007 (English)In: 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) Published
    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.

    Keywords
    Nostoc punctiforme, isolation, membranes, thylakoids, proteomics, photosystem II, photosystem I
    National Category
    Chemical Sciences Biological Sciences
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:uu:diva-12478 (URN)10.1111/j.1399-3054.2007.00982.x (DOI)000250763500010 ()18251853 (PubMedID)
    Available from: 2012-05-08 Created: 2007-12-27 Last updated: 2017-12-11Bibliographically approved
    2. Quantitative shotgun proteomics of enriched heterocysts from Nostoc sp. PCC 7120 using 8-Plex isobaric peptide tags
    Open this publication in new window or tab >>Quantitative shotgun proteomics of enriched heterocysts from Nostoc sp. PCC 7120 using 8-Plex isobaric peptide tags
    Show others...
    2008 (English)In: Journal of Proteome Research, ISSN 1535-3893, E-ISSN 1535-3907, Vol. 7, no 4, p. 1615-1628Article in journal (Refereed) Published
    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.

    Keywords
    8-plex, iTRAQ, proteomics, Nostoc sp PCC 7120, Tandem-MS, nitrogen fixation, cyanobacteria, nitrogen fixation, heterocyst, Proteome
    National Category
    Biochemistry and Molecular Biology
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:uu:diva-108461 (URN)10.1021/pr700604v (DOI)000254711000026 ()
    Available from: 2012-05-08 Created: 2009-09-18 Last updated: 2017-12-13
    3. Quantitative overview of N2 fixation in Nostoc punctiforme ATCC 29133 through cellular enrichments and iTRAQ shotgun proteomics
    Open this publication in new window or tab >>Quantitative overview of N2 fixation in Nostoc punctiforme ATCC 29133 through cellular enrichments and iTRAQ shotgun proteomics
    Show others...
    2009 (English)In: Journal of Proteome Research, ISSN 1535-3893, E-ISSN 1535-3907, Vol. 8, no 1, p. 187-198Article in journal (Refereed) Published
    Abstract [en]

    Nostoc punctiforme ATCC 29133 is a photoautotrophic cyanobacterium with the capacity to fix atmospheric N2. Its ability to mediate this process is similar to that described for Nostoc sp. PCC 7120, where vegetative cells differentiate into heterocysts. Quantitative proteomic investigations at both the filament level and the heterocyst level are presented using isobaric tagging technology (iTRAQ), with 721 proteins at the 95% confidence interval quantified across both studies. Observations from both experiments yielded findings confirmatory of both transcriptional studies, and published Nostoc sp. PCC 7120 iTRAQ data. N. punctiforme exhibits similar metabolic trends, though changes in a number of metabolic pathways are less pronounced than in Nostoc sp. PCC 7120. Results also suggest a number of proteins that may benefit from future investigations. These include ATP dependent Zn-proteases, N-reserve degraders and also redox balance proteins. Complementary proteomic data sets from both organisms present key precursor knowledge that is important for future cyanobacterial biohydrogen research.

    Place, publisher, year, edition, pages
    USA: ACS Publications, 2009
    Keywords
    iTRAQ, Shotgun proteomics, Nostoc punctiforme ATCC 29133, Nostoc sp PCC 73102, Tandem-MS, Dinitrogen Fixation, Heterocysts
    National Category
    Chemical Sciences
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:uu:diva-108462 (URN)10.1021/pr800285v (DOI)000262171100021 ()
    Available from: 2009-09-18 Created: 2009-09-18 Last updated: 2017-12-13
    4. Electron transfer protein complexes in the thylakoid membranes of heterocysts from the cyanobacterium Nostoc punctiforme
    Open this publication in new window or tab >>Electron transfer protein complexes in the thylakoid membranes of heterocysts from the cyanobacterium Nostoc punctiforme
    Show others...
    2009 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1787, no 4, p. 252-263Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    Elsevier, 2009
    Keywords
    Cyanobacteria, Nostoc, Heterocyst, Photosystem II, Fluorescence, BN-PAGE
    National Category
    Biochemistry and Molecular Biology
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:uu:diva-108433 (URN)10.1016/j.bbabio.2009.01.015 (DOI)000264575700005 ()
    Available from: 2012-05-08 Created: 2009-09-18 Last updated: 2017-12-13
    5. Excitation energy transfer to Photosystem I in filaments and heterocysts of Nostoc punctiforme
    Open this publication in new window or tab >>Excitation energy transfer to Photosystem I in filaments and heterocysts of Nostoc punctiforme
    2010 (English)In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1797, no 3, p. 425-433Article in journal (Refereed) Published
    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.

    Keywords
    heterocyst, photosystem I, energy transfer, excitation, Nosotc punctiforme, phycobilisome, photosystem II
    National Category
    Biochemistry and Molecular Biology
    Research subject
    Biochemistry
    Identifiers
    urn:nbn:se:uu:diva-108463 (URN)10.1016/j.bbabio.2009.12.014 (DOI)000274772900010 ()20036211 (PubMedID)
    Available from: 2012-05-08 Created: 2009-09-18 Last updated: 2017-12-13Bibliographically approved
  • 47.
    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.

  • 48.
    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.

  • 49.
    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.

  • 50. Chaignon, Frederique
    et al.
    Blart, Errol
    Borgström, Magnus
    Hammarström, Leif
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Photochemistry and Molecular Science. Physics, Department of Physics and Materials Science, Chemical Physics.
    Odobel, Fabrice
    Design of molecular architectures to mimic photosynthesis2006In: Actualite Chimique, Vol. 297, p. 23-27Article in journal (Refereed)
123456 1 - 50 of 280
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