uu.seUppsala University Publications
Change search
Refine search result
12 1 - 50 of 89
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the 'Create feeds' function.
  • 1.
    Ahmadova, Nigar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ho, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Tyrosine D oxidation and redox equilibrium in Photosystem II2017In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1858, no 6, p. 407-417Article in journal (Refereed)
    Abstract [en]

    Tyrosine ID (Tyr(D)) is an auxiliary redox active tyrosine residue in photosystem II (PSII). The mechanism of Tyr(D) oxidation was investigated by EPR spectroscopy, flash-induced fluorescence decay and thermoluminescence measurements in PSII enriched membranes from spinach. PSII membranes were chemically treated with 3 mM ascorbate and 1 mM diaminodurene and subsequent washing, leading to the complete reduction of Tyr(D). Tyr(D) oxidation kinetics and competing recombination reactions were measured after a single saturating flash in the absence and presence of DCMU (inhibitor of the Q(B)-site) in the pH range of 4.7-8.5. Two kinetic phases of Tyro oxidation were observed by the time resolved EPR spectroscopy the fast phase (msec-sec time range) and the pH dependent slow phase (tens of seconds time range). In the presence of DCMU, Tyr(D) oxidation kinetics was monophasic in the entire pH range, i.e. only the fast kinetics was observed. The results obtained from the fluorescence and thermoluminescence analysis show that when forward electron transport is blocked in the presence of DCMU, the S(2)Q((S) over bar) recombination outcompetes the slow phase of Tyr(D) oxidation by the S-2 state. Modelling of the whole complex of these electron transfer events associated with Tyr(D) oxidation fitted very well with our experimental data. Based on these data, structural information and theoretical considerations we confirm our assignment of the fast and slow oxidation kinetics to two populations of PSII centers with different water positions (proximal and distal) in the Tyr(D) vicinity.

  • 2.
    Ahmadova, Nigar
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Formation of tyrosine radicals in photosystem II under far-red illumination2018In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 136, no 1, p. 93-106Article in journal (Refereed)
    Abstract [en]

    Photosystem II (PS II) contains two redox-active tyrosine residues on the donor side at symmetrical positions to the primary donor, P680. TyrZ, part of the water-oxidizing complex, is a preferential fast electron donor while TyrD is a slow auxiliary donor to P680 +. We used PS II membranes from spinach which were depleted of the water oxidation complex (Mn-depleted PS II) to study electron donation from both tyrosines by time-resolved EPR spectroscopy under visible and far-red continuous light and laser flash illumination. Our results show that under both illumination regimes, oxidation of TyrD occurs via equilibrium with TyrZ at pH 4.7 and 6.3. At pH 8.5 direct TyrD oxidation by P680 + occurs in the majority of the PS II centers. Under continuous far-red light illumination these reactions were less effective but still possible. Different photochemical steps were considered to explain the far-red light-induced electron donation from tyrosines and localization of the primary electron hole (P680 +) on the ChlD1 in Mn-depleted PS II after the far-red light-induced charge separation at room temperature is suggested.

  • 3. 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.

  • 4. Allahverdiyeva, Yagut
    et al.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Mäenpää, Pirkko
    Vass, Imre
    Aro, Eva-Mari
    Modulation of photosynthetic electron transport in the absence of terminal electron acceptors: characterization of the rbcL deletion mutant of tobacco2005In: Biochimica et Biophysica Acta (BBA) - Bioenergetics, ISSN 0005-2728, Vol. 1709, no 1, p. 69-83Article in journal (Refereed)
  • 5. 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.

  • 6.
    Chen, Guiying
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Allahverdiyeva, Yagut
    Aro, Eva-Mari
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Electron paramagnetic resonance study of the electron transfer reactions in photosystem II membrane preparations from Arabidopsis thaliana2011In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1807, no 2, p. 205-215Article in journal (Refereed)
    Abstract [en]

    Arabidopsis thaliana is widely used as a model organism in plant biology as its genome has been sequenced and transformation is known to be efficient. A large number of mutant lines and genomic resources are available for Arabidopsis. All this makes Arabidopsis a useful tool for studies of photosynthetic reactions in higher plants. In this study, photosystem II (PSII) enriched membranes were successfully isolated from thylakoids of Arabidopsis plants and for the first time the electron transfer cofactors in PSII were systematically studied using electron paramagnetic resonance (EPR) spectroscopy. EPR signals from both of the donor and acceptor sides of PSII, as well as from auxiliary electron donors were recorded. From the acceptor side of PSII, EPR signals from Q(A)(-)Fe(2+) and Phe(-)Q(A)(-)Fe(2+) as well as from the free Phe(-) radical were observed. The multiline EPR signals from the S-0- and S-2-states of CaMn4Ox-cluster in the water oxidation complex were characterized. Moreover, split EPR signals, the interaction signals from Y-Z center dot and CaMn4Ox-cluster in the S-0-, S-1-, S-2-, and the S-3-state were induced by illumination of the PSII membranes at 5 K and characterized. In addition, EPR signals from auxiliary donors Y-D center dot, Chl(+) and cytochrome b(559) were observed. In total, we were able to detect about 20 different EPR signals covering all electron transfer components in PSII. Use of this spectroscopic platform opens a possibility to study PSII reactions in the library of mutants available in Arabidopsis.

  • 7.
    Chen, Guiying
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Han, Guangye
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Göransson, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Stability of the S(3) and S(2) State Intermediates in Photosystem II Directly Probed by EPR Spectroscopy2012In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 51, no 1, p. 138-148Article in journal (Refereed)
    Abstract [en]

    The stability of the S(3) and S(2) states of the oxygen evolving complex in photosystem II (PSII) was directly probed by EPR spectroscopy in PSII membrane preparations from spinach in the presence of the exogenous electron acceptor PpBQ at 1, 10, and 20 degrees C. The decay of the S(3) state was followed in samples exposed to two flashes by measuring the split S(3) EPR signal induced by near-infrared illumination at 5 K. The decay of the S(2) state was followed in samples exposed to one flash by measuring the S(2) state multiline EPR signal. During the decay of the S(3) state, the S(2) state multiline EPR signal first increased and then decreased in amplitude. This shows that the decay of the S(3) state to the S(1) state occurs via the S(2) state. The decay of the S(3) state was biexponential with a fast kinetic phase with a few seconds decay half-time. This occurred in 10-20% of the PSII centers. The slow kinetic phase ranged from a decay half-time of 700 s (at 1 degrees C) to similar to 100 s (at 20 degrees C) in the remaining 80-90% of the centers. The decay of the S(2) state was also biphasic and showed quite similar kinetics to the decay of the S(3) state. Our experiments show that the auxiliary electron donor Y(D) was oxidized during the entire experiment. Thus, the reduced form of Y(D) does not participate to the fast decay of the S(2) and S(3) states we describe here. Instead, we suggest that the decay of the S(3) and S(2) states reflects electron transfer from the acceptor side of PSII to the donor side of PSII starting in the corresponding S state. It is proposed that this exists in equilibrium with Y(Z) according to S(3)Y(2) double left right arrow S(2)Y(Z)(.) in the case of the S(3) state decay and S(2)Y(Z) double left right arrow S(1)Y(Z)(.) in the case of the S(2) state decay. Two kinetic models are discussed, both developed with the assumption that the slow decay of the S(3) and S(2) states occurs in PSII centers where Y(Z) is also a fast donor to P(680)(+) working in the nanosecond time regime and that the fast decay of the S(3) and S(2) states occurs in centers where Y(Z) reduces P(680)(+) with slower microsecond kinetics. Our measurements also demonstrate that the split S(3) EPR signal can be used as a direct probe to the S(3) state and that it can provide important information about the redox properties of the S(3) state.

  • 8.
    Cieslak, Anna M.
    et al.
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland..
    Pavliuk, Mariia V.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    D'Amario, Luca
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Abdellah, Mohamed
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sokolowski, Kamil
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland..
    Rybinska, Urszula
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Fernandes, Daniel L. A.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Leszczynski, Michal K.
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland..
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    El-Zhory, Ahmed M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Föhlinger, Jens
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Budinska, Alena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Wolska-Pietkiewicz, Malgorzata
    Warsaw Univ Technol, Fac Chem, PL-00661 Warsaw, Poland..
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lewinski, Janusz
    Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland.;Warsaw Univ Technol, Fac Chem, PL-00661 Warsaw, Poland..
    Sá, Jacinto
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Polish Acad Sci, Inst Phys Chem, PL-01224 Warsaw, Poland..
    Ultra long-lived electron-hole separation within water-soluble colloidal ZnO nanocrystals: Prospective Applications For Solar Energy Production2016In: Nano Energy, ISSN 2211-2855, Vol. 30, p. 187-192Article in journal (Refereed)
    Abstract [en]

    Zinc oxide was one of the first semiconductors used in dye-sensitized solar cells but its instability in aqueous media precludes its use for large-scale applications. Herein, we report on a novel ZnO nanocrystal material derived by an organometallic approach that is simultaneously stable and soluble in water due to its carboxylate oligoethylene glycol shell strongly anchored to the inorganic core by the head groups. The resulting unique inorganic core-organic shell interface also stabilizes the photo-generated hole, leading to a dramatic slowing down of charge recombination, which otherwise is a major hurdle in using nanostructured ZnO.

  • 9.
    Daniel, Quentin
    et al.
    KTH Royal Inst Technol.
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Fan, Ting
    KTH Royal Inst Technol.
    Wang, Ying
    KTH Royal Inst Technol.
    Duan, Lele
    KTH Royal Inst Technol.
    Wang, Lei
    KTH Royal Inst Technol.
    Li, Fusheng
    KTH Royal Inst Technol.
    Rinkevicius, Zilvinas
    KTH Royal Inst Technol.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Ahlquist, Marten S. G.
    KTH Royal Inst Technol.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Sun, Licheng
    KTH Royal Inst Technol; Dalian Univ Technol.
    Rearranging from 6-to 7-coordination initiates the catalytic activity: An EPR study on a Ru-bda water oxidation catalyst2017In: Coordination chemistry reviews, ISSN 0010-8545, E-ISSN 1873-3840, Vol. 346, p. 206-215Article, review/survey (Refereed)
    Abstract [en]

    The coordination of a substrate water molecule on a metal centered catalyst for water oxidation is a crucial step involving the reorganization of the ligand sphere. This process can occur by substituting a coordinated ligand with a water molecule or via a direct coordination of water onto an open site. In 2009, we reported an efficient ruthenium-based molecular catalyst, Ru-bda, for water oxidation. Despite the impressive improvement in catalytic activity of this type of catalyst over the past years, a lack of understanding of the water coordination still remains. Herein, we report our EPR and DFT studies on Ru-bda (triethylammonium 3-pyridine sulfonate)(2) (1) at its Ru-III oxidation state, which is the initial state in the catalytic cycle for the O-O bond formation. Our investigation suggests that at this III-state, there is already a rearrangement in the ligand sphere where the coordination of a water molecule at the 7th position (open site) takes place under acidic conditions (pH = 1.0) to form a rare 7-coordinated Ru-III species.

  • 10. Danielsson, Ravi
    et al.
    Albertsson, Per-Åke
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Styring, Stenbjörn
    Quantification of photosystem I and II in different parts of the thylakoid membrane2004In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1608, p. 53-61Article in journal (Refereed)
  • 11. Danielsson, Ravi
    et al.
    Suorsa, Marjaana
    Paakkarinen, Virpi
    Albertsson, Per-Ake
    Styring, Stenbjörn
    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.
    Aro, Eva-Mari
    Mamedov, Fikret
    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.
    Dimeric and monomeric organization of photosystem II. Distribution of five distinct complexes in the different domains of the thylakoid membrane.2006In: J Biol Chem, ISSN 0021-9258, Vol. 281, no 20, p. 14241-9Article in journal (Refereed)
  • 12. Fristedt, Rikard
    et al.
    Herdean, Andrei
    Blaby-Haas, Crysten
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Merchant, Sabeeha
    Last, Robert
    Lundin, Robert
    Photosystem II protein 33, a protein conserved in the plastid lineage, is associated with the chloroplast thylakoid membrane and provides stability to photosystem II supercomplexes in Arabidopsis2015In: Plant Physiology, ISSN 0032-0889, E-ISSN 1532-2548, Vol. 167, no 2, p. 481-492Article in journal (Refereed)
    Abstract [en]

    Photosystem II (PSII) is a multiprotein complex that catalyzes the light-driven water-splitting reactions of oxygenic photosynthesis. Light absorption by PSII leads to the production of excited states and reactive oxygen species that can cause damage to this complex. Here, we describe Arabidopsis (Arabidopsis thaliana) At1g71500, which encodes a previously uncharacterized protein that is a PSII auxiliary core protein and hence is named PHOTOSYSTEM II PROTEIN33 (PSB33). We present evidence that PSB33 functions in the maintenance of PSII-light-harvesting complex II (LHCII) supercomplex organization. PSB33 encodes a protein with a chloroplast transit peptide and one transmembrane segment. In silico analysis of PSB33 revealed a light-harvesting complex-binding motif within the transmembrane segment and a large surface-exposed head domain. Biochemical analysis of PSII complexes further indicates that PSB33 is an integral membrane protein located in the vicinity of LHCII and the PSII CP43 reaction center protein. Phenotypic characterization of mutants lacking PSB33 revealed reduced amounts of PSII-LHCII supercomplexes, very low state transition, and a lower capacity for nonphotochemical quenching, leading to increased photosensitivity in the mutant plants under light stress. Taken together, these results suggest a role for PSB33 in regulating and optimizing photosynthesis in response to changing light levels.

  • 13. Gadjieva, Rena
    et al.
    Mamedov, Fikret
    Conversion of the low potential form of cytochrome b559 into the high potential form in photosystem II under anaerobic and reducing conditions1998In: Photosynthesis: Mechanisms and Effects / [ed] Garab, G., Kluwer Academic Publishers, 1998, p. 1101-1104Conference paper (Refereed)
  • 14. Gadjieva, Rena
    et al.
    Mamedov, Fikret
    Albertsson, Per-Åke
    Styring, Stenbjörn
    Fractionation of the thylakoid membranes from tobacco. A tentative isolation of “end membrane” and purified “stroma lamellae” membranes1999In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1411, p. 92-100Article in journal (Refereed)
  • 15. Gadjieva, Rena
    et al.
    Mamedov, Fikret
    Renger, Gernot
    Styring, Stenbjörn
    Interconversion of low and high potential forms of cytochrome b559 in tris-washed photosystem II membranes under aerobic/anaerobic conditions1999In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Biochem, Vol. 38, p. 10578-10584Article in journal (Refereed)
  • 16. Gasanov, R.A.
    et al.
    Gadjieva, R.M.
    Mamedov, Fikret
    Light induced inhibition of oxygen evolution of photosystem II1991In: Photosynthesis and Photobiotechnology / [ed] Kefeli, V.I., Pushino , 1991, p. 78-79Conference paper (Refereed)
  • 17. Gasanov, Ralphreed
    et al.
    Aliyeva, Samira
    Arao, Sachiko
    Ismailova, Aygun
    Katsuta, Nobuhiro
    Kitade, Hidetoshi
    Yamada, Shuji
    Kawamori, Asako
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Comparative study of the water oxidizing reactions and the millisecond delayed chlorophyll fluorescence in photosystem II at different pH2007In: Journal of Photochemistry and Photobiology. B: Biology, ISSN 1011-1344, E-ISSN 1873-2682, Vol. 86, no 2, p. 160-164Article in journal (Refereed)
    Abstract [en]

    Water splitting activity, the multiline EPR signal associated with S2-state of the CaMn4-cluster and the fast and slow phases of the induction curve of the millisecond delayed chlorophyll fluorescence from photosystem II (PSII) in the pH range of 4.5–8.5 were studied in the thylakoid membranes and purified PSII particles. It has been found that O2 evolution and the multiline EPR signal were inhibited at acidic (pK 5.3) and alkaline (pK 8.1) pH values, and were maximal at pH 6.0–7.0. Our results indicate that the loss of O2 evolution and the S2-state multiline EPR signal associated with the decrease of the millisecond delayed chlorophyll fluorescence only in alkaline region (pH 7.0–8.5). Possible correlations of the millisecond delayed chlorophyll fluorescence components with the donor side reactions in PSII are discussed.

  • 18. Gasanov, Ralphreed
    et al.
    Aliyeva, Samira
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Delayed fluorescence in a millisecond range: a probe for the donor side-induced photoinhibition in photosystem II2015In: Photosynthesis: Basics to applications / [ed] S. Itoh, P. Mohanty, K.N. Guruprasad, New Delhi, India: I.K. International Publishing House Pvt. Ltd. , 2015, p. 101-107Chapter in book (Refereed)
  • 19. Grasse, Nicole
    et al.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Becker, Kristin
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Roegner, Matthias
    Nowaczyk, Marc M.
    Role of Novel Dimeric Photosystem II (PSII)-Psb27 Protein Complex in PSII Repair2011In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 286, no 34, p. 29548-29555Article in journal (Refereed)
    Abstract [en]

    The multisubunit membrane protein complex Photosystem II (PSII) catalyzes one of the key reactions in photosynthesis: the light-driven oxidation of water. Here, we focus on the role of the Psb27 assembly factor, which is involved in biogenesis and repair after light-induced damage of the complex. Weshow that Psb27 is essential for the survival of cyanobacterial cells grown under stress conditions. The combination of cold stress (30 degrees C) and high light stress (1000 mu mol of photons x m(-2) x s(-1)) led to complete inhibition of growth in a Delta psb27 mutant strain of the thermophilic cyanobacterium Thermosynechococcus elongatus, whereas wild-type cells continued to grow. Moreover, Psb27-containing PSII complexes became the predominant PSII species in preparations from wild-type cells grown under cold stress. Two different PSII-Psb27 complexes were isolated and characterized in this study. The first complex represents the known monomeric PSII-Psb27 species, which is involved in the assembly of PSII. Additionally, a novel dimeric PSII-Psb27 complex could be allocated in the repair cycle, i.e. in processes after inactivation of PSII, by (15)N pulse-label experiments followed by mass spectrometry analysis. Comparison with the corresponding PSII species from Delta psb27 mutant cells showed that Psb27 prevented the release of manganese from the previously inactivated complex. These results indicate a more complex role of the Psb27 protein within the life cycle of PSII, especially under stress conditions.

  • 20.
    Han, Guangye
    et al.
    Institute of Botany, The Chinese Academy of Sciences.
    Ho, Felix M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Havelius, Kajsa G. V.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Morvaridi, Susan F.
    Department of Chemistry and Biochemistry, University of California-Los Angeles,.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Direct quantification of the four individual S states in Photosystem II using EPR spectroscopy2008In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1777, no 6, p. 496-503Article in journal (Refereed)
    Abstract [en]

    Car, carotenoid; Chl, chlorophyll; ChlZ, secondary chlorophyll electron donor to P680+; Cytb559, cytochrome b559; EPR, electron paramagnetic resonance; DMSO, dimethylsulfoxide; MES, 2-(N-morpholino) ethanesulfonic acid; NIR, near-infrared; OEC, oxygen evolving complex; P680, primary electron donor chlorophylls in PSII; PpBQ, phenyl-p-benzoquinone; PSII, Photosystem II; QA and QB, primary and secondary plastoquinone acceptors of Photosystem II; YD, tyrosine 161 of the PSII D2 polypeptide; YZ, tyrosine 161 of the PSII D1 polypeptide

  • 21. Han, Guangye
    et al.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Misses during Water Oxidation in Photosystem II Are S State-dependent2012In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 287, no 16, p. 13422-13429Article in journal (Refereed)
    Abstract [en]

    The period of four oscillation of the S state intermediates of the water oxidizing complex in Photosystem II (PSII) is commonly analyzed by the Kok parameters. The important miss factor determines the efficiency for each S transition. Commonly, an equal miss factor has been used in the analysis. We have used EPR signals which probe all S states in the same sample during S cycle advancement. This allows, for the first time, to measure directly the miss parameter for each S state transition. Experiments were performed in PSII membrane preparations from spinach in the presence of electron acceptor at 1 degrees C and 20 degrees C. The data show that the miss parameter is different in different transitions and shows different temperature dependence. We found no misses at 1 degrees C and 10% misses at 20 degrees C during the S-1 -> S-2 transition. The highest miss factor was found in the S-2 -> S-3 transition which decreased from 23% to 16% with increasing temperature. For the S-3 -> S-0 transition the miss parameter was found to be 7% at 1 degrees C and decreased to 3% at 20 degrees C. For the S-0 -> S-1 transition the miss parameter was found to be approximately 10% at both temperatures. The contribution from the acceptor side in the form of recombination reactions as well as from the donor side of PSII to the uneven misses is discussed. It is suggested that the different transition efficiency in each S transition partly reflects the chemistry at the CaMn4O5 cluster. That consequently contributes to the uneven misses during S cycle turnover in PSII.

  • 22. Han, Guangye
    et al.
    Morvaridi, Susan
    Ho, Felix
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    S-state dependence of misses in the OEC probed by EPR spectroscopy of individual S-states2008In: Photosynthesis. Energy from the Sun / [ed] Allen J.F., Gant E., Golbeck J.H. and Osmond B., Springer , 2008, p. 419-422Conference paper (Refereed)
  • 23.
    Havelius, Kajsa G. V.
    et al.
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    Ho, Felix M.
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    Su, Ji-Hu
    Max Plank Institute for Bioinorganic Chemistry.
    Han, Guangye
    Institute of Botany, The Chinese Academy of Sciences.
    Mamedov, Fikret
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    The same origin of the split EPR signal induced by visible or near-infrared light at liquid helium temperature from the S3-state of photosystem IIManuscript (Other academic)
  • 24.
    Havelius, Kajsa G. V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Sjöholm, Johannes
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ho, Felix M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Metalloradical EPR Signals from the Y-Z center dot S-State Intermediates in Photosystem II2010In: Applied Magnetic Resonance, ISSN 0937-9347, E-ISSN 1613-7507, Vol. 37, no 1-4, p. 151-176Article, review/survey (Refereed)
    Abstract [en]

    The redox-active tyrosine residue (Y-Z) plays a crucial role in the mechanism of the water oxidation. Metalloradical electron paramagnetic resonance (EPR) signals reflecting the light-induced Y-Z center dot in magnetic interaction with the CaMn4-cluster in the particular S-state, Y-Z center dot S-X intermediates, have been found in intact photosystem II. These so-called split EPR signals are induced by illumination at cryogenic temperatures and provide means to both study the otherwise transient Y-Z center dot and to probe the S-states with EPR spectroscopy. The illumination used for signal induction grouped the observed split EPR signals in two categories: (i) Y-Z in the lower S-states was oxidized by P680(+) formed via charge separation, while (ii) Y-Z in the higher S-states was oxidized by an excited, highly oxidizing Mn species. Applied mechanistic studies of the Y-Z center dot S-X intermediates in the different S-states are reviewed and compared to investigations in photosystem II at physiological temperature. Addition of methanol induced S-state characteristic changes in the split signals' formation which reflect changes in the magnetic coupling within the CaMn4-cluster due to methanol binding. The pH titration of the split EPR signals, on the other hand, could probe the proton-coupled electron transfer properties of the Y-Z oxidation. The apparent pK (a)s found for decreased split signal induction were interpreted in the fate of the phenol proton.

  • 25. Havelius, Kajsa G V
    et al.
    Su, Ji-Hu
    Feyziyev, Yashar
    Mamedov, Fikret
    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.
    Styring, Stenbjörn
    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.
    Spectral resolution of the split EPR signals induced by illumination at 5 K from the S1, S3, and S0 states in photosystem II.2006In: Biochemistry, ISSN 0006-2960, Vol. 45, no 30, p. 9279-90Article in journal (Refereed)
  • 26.
    Havelius, Kajsa G. V.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Su, Ji-Hu
    Han, Guangye
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Ho, Felix M.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    The formation of the split EPR signal from the S-3 state of Photosystem II does not involve primary charge separation2011In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1807, no 1, p. 11-21Article in journal (Refereed)
    Abstract [en]

    Metalloradical EPR signals have been found in intact Photosystem II at cryogenic temperatures. They reflect the light-driven formation of the tyrosine Z radical (Y-z(center dot)) in magnetic interaction with the CaMn4 cluster in a particular S state. These so-called split EPR signals, induced at cryogenic temperatures, provide means to study the otherwise transient Y-z(center dot) and to probe the S states with EPR spectroscopy. In the S-0 and S-1 states, the respective split signals are induced by illumination of the sample in the visible light range only. In the S-3 state the split EPR signal is induced irrespective of illumination wavelength within the entire 415-900 nm range (visible and near-IR region) [Su, J. H., Havelius, K. G. V., Ho, F. M., Han, G., Mamedov, F., and Styring, S. (2007) Biochemistry 46. 10703-10712]. An important question is whether a single mechanism can explain the induction of the Split S-3 signal across the entire wavelength range or whether wavelength-dependent mechanisms are required. In this paper we confirm that the Y-z(center dot) radical formation in the S-1 state, reflected in the Split S-1 signal, is driven by P680-centered charge separation. The situation in the S-3 state is different. In Photosystem II centers with pre-reduced quinone A (Q(A)), where the P680-centered charge separation is blocked, the Split S-3 EPR signal could still be induced in the majority of the Photosystem II centers using both visible and NIR (830 nm) light. This shows that P680-centered charge separation is not involved. The amount of oxidized electron donors and reduced electron acceptors (Q(A)(-)) was well correlated after visible light illumination at cryogenic temperatures in the S-1 state. This was not the case in the S-3 state, where the Split S-3 EPR signal was formed in the majority of the centers in a pathway other than P680-centered charge separation. Instead, we propose that one mechanism exists over the entire wavelength interval to drive the formation of the Split S-3 signal. The origin for this, probably involving excitation of one of the Mn ions in the CaMn4 cluster in Photosystem II, is discussed.

  • 27. Havelius, Kajsa
    et al.
    Su, Ji-Hu
    Ho, Felix
    Han, Guangye
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    The mechanism behind the formation of the “Split S3” EPR signal in photosystem II induced by visible or near-infrared light2008In: Photosynthesis. Energy from the Sun / [ed] Allen J.F., Gant E., Golbeck J.H. and Osmond B., Springer , 2008, p. 423-426Conference paper (Refereed)
  • 28.
    Ho, Felix M.
    et al.
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    Havelius, Kajsa G. V.
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    Sjöholm, Johannes
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    Mamedov, Fikret
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    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 Photochemistry and Molecular Science, Molecular Biomimetics.
    Investigation and characterisation of EPR split signals in the native S2 state of Photosystem IIManuscript (Other academic)
  • 29.
    Ho, Felix M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Morvaridi, Susan F.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Enhancement of Y-D(center dot) spin relaxation by the CaMn4 cluster in photosystem II detected at room temperature: A new probe for the S-cycle2007In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1767, no 1, p. 5-14Article in journal (Refereed)
    Abstract [en]

    The long-lived, light-induced radical Y-D(.) of the Tyr161 residue in the D2 protein of Photosystem 11 (PSII) is known to magnetically interact with the CaMn4 cluster, situated similar to 30 angstrom away. In this study we report a transient step-change increase in YD EPR intensity upon the application of a single laser flash to S, state-synchronised PSII-enriched membranes from spinach. This transient effect was observed at room temperature and high applied microwave power (100 mW) in samples containing PpBQ, as well as those containing DCMU. The subsequent decay lifetimes were found to differ depending on the additive used. We propose that this flash-induced signal increase was caused by enhanced spin relaxation of YD by the OEC in the S-2 state, as a consequence of the single laser flash turnover. The post-flash decay reflected S-2 -> S-1 back-turnover, as confirmed by their correlations with independent measurements of S-2 multiline EPR signal and flash-induced variable fluorescence decay kinetics under corresponding experimental conditions. This flash-induced effect opens up the possibility to study the kinetic behaviour of S-state transitions at room temperature using YD as a probe.

  • 30.
    Huang, Hao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Karlsson, Christoffer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Gogoll, A
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Organic Chemistry.
    Sjödin, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. Waseda Univ, Dept Appl Chem, Tokyo 1698555, Japan..
    Polaron Disproportionation Charge Transport in a Conducting Redox Polymer2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 24, p. 13078-13083Article in journal (Refereed)
    Abstract [en]

    Herein we report a mechanistic study of the charge transport in poly-3-((2,5-hydroquinone)vinyl)-1H-pyrrole by conductance measurements at various temperatures performed in situ during doping of the polypyrrole backbone in contact with an aqueous electrolyte. Charge transport was found to occur by electron hopping with associated electron transfer activation energies in the range of 0.08-0.2 eV. In situ electron paramagnetic resonance experiments indicated polarons as the dominant charge carriers and the charge transport was found to follow a second-order dependence with respect to the number of accumulated charges. Based on the findings, we present a polaron comproportionation/disproportionation model for electron conduction in poly-3-((2,5-hydroquinone)vinyl)-1H-pyrrole, thus, providing a complement to existing models for charge propagation in conducting polymers.

  • 31.
    Jarvi, Sari
    et al.
    Univ Turku, Dept Biochem, Mol Plant Biol, SF-20500 Turku, Finland..
    Isojarvi, Janne
    Univ Turku, Dept Biochem, Mol Plant Biol, SF-20500 Turku, Finland..
    Kangasjarvi, Saijaliisa
    Univ Turku, Dept Biochem, Mol Plant Biol, SF-20500 Turku, Finland..
    Salojarvi, Jarkko
    Univ Helsinki, Dept Biosci, Plant Biol, Helsinki, Finland..
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Suorsa, Marjaana
    Univ Turku, Dept Biochem, Mol Plant Biol, SF-20500 Turku, Finland..
    Aro, Eva-Mari
    Univ Turku, Dept Biochem, Mol Plant Biol, SF-20500 Turku, Finland..
    Photosystem II Repair and Plant Immunity: Lessons Learned from Arabidopsis Mutant Lacking the THYLAKOID LUMEN PROTEIN 18.32016In: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 7, article id 405Article in journal (Refereed)
    Abstract [en]

    Chloroplasts play an important role in the cellular sensing of abiotic and biotic stress. Signals originating from photosynthetic light reactions, in the form of redox and pH changes, accumulation of reactive oxygen and electrophile species or stromal metabolites are of key importance in chloroplast retrograde signaling. These signals initiate plant acclimation responses to both abiotic and biotic stresses. To reveal the molecular responses activated by rapid fluctuations in growth light intensity, gene expression analysis was performed with Arabidopsis thaliana wild type and the tlp18.3 mutant plants, the latter showing a stunted growth phenotype under fluctuating light conditions (Biochem. J, 406, 415-425). Expression pattern of genes encoding components of the photosynthetic electron transfer chain did not differ between fluctuating and constant light conditions, neither in wild type nor in tlp18.3 plants, and the composition of the thylakoid membrane protein complexes likewise remained unchanged. Nevertheless, the fluctuating light conditions repressed in wild-type plants a broad spectrum of genes involved in immune responses, which likely resulted from shade-avoidance responses and their intermixing with hormonal signaling. On the contrary, in the tlp18.3 mutant plants there was an imperfect repression of defense-related transcripts upon growth under fluctuating light, possibly by signals originating from minor malfunction of the photosystem II (PSII) repair cycle, which directly or indirectly modulated the transcript abundances of genes related to light perception via phytochromes. Consequently, a strong allocation of resources to defense reactions in the tlp18.3 mutant plants presumably results in the stunted growth phenotype under fluctuating light.

  • 32. Järvi, Sari
    et al.
    Isojärvi, Janne
    Kangasjärvi, Säijaliisa
    Salojärvi, Jarkko
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Suorsa, Marjaana
    Aro, Eva-Mari
    Photosystem II repair and plant immunity: Lessons learned from Arabidopsis mutant lacking the thylakoid lumen protein 18.32016In: Frontiers in Plant Science, ISSN 1664-462X, E-ISSN 1664-462X, Vol. 7, article id 405Article in journal (Refereed)
    Abstract [en]

    Chloroplasts play an important role in the cellular sensing of abiotic and biotic stress. Signals originating from photosynthetic light reactions, in the form of redox and pH changes, accumulation of reactive oxygen and electrophile species or stromal metabolites are of key importance in chloroplast retrograde signaling. These signals initiate plant acclimation responses to both abiotic and biotic stresses. To reveal the molecular responses activated by rapid fluctuations in growth light intensity, gene expression analysis was performed with Arabidopsis thaliana wild type and the tlp18.3 mutant plants, the latter showing a stunted growth phenotype under fluctuating light conditions (Biochem. J, 406, 415–425). Expression pattern of genes encoding components of the photosynthetic electron transfer chain did not differ between fluctuating and constant light conditions, neither in wild type nor in tlp18.3 plants, and the composition of the thylakoid membrane protein complexes likewise remained unchanged. Nevertheless, the fluctuating light conditions repressed in wild-type plants a broad spectrum of genes involved in immune responses, which likely resulted from shade-avoidance responses and their intermixing with hormonal signaling. On the contrary, in the tlp18.3 mutant plants there was an imperfect repression of defense-related transcripts upon growth under fluctuating light, possibly by signals originating from minor malfunction of the photosystem II (PSII) repair cycle, which directly or indirectly modulated the transcript abundances of genes related to light perception via phytochromes. Consequently, a strong allocation of resources to defense reactions in the tlp18.3 mutant plants presumably results in the stunted growth phenotype under fluctuating light.

  • 33. Karonen, Maarit
    et al.
    Mattila, Heta
    Huang, Ping
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Tyystjarvi, Esa
    A Tandem Mass Spectrometric Method for Singlet Oxygen Measurement2014In: Photochemistry and Photobiology, ISSN 0031-8655, E-ISSN 1751-1097, Vol. 90, no 5, p. 965-971Article in journal (Refereed)
    Abstract [en]

    Singlet oxygen, a harmful reactive oxygen species, can be quantified with the substance 2,2,6,6-tetramethylpiperidine (TEMP) that reacts with singlet oxygen, forming a stable nitroxyl radical (TEMPO). TEMPO has earlier been quantified with electron paramagnetic resonance (EPR) spectroscopy. In this study, we designed an ultra-high-performance liquid chromatographictandem mass spectrometric (UHPLC-ESI-MS/MS) quantification method for TEMPO and showed that the method based on multiple reaction monitoring (MRM) can be used for the measurements of singlet oxygen from both nonbiological and biological samples. Results obtained with both UHPLC-ESI-MS/MS and EPR methods suggest that plant thylakoid membranes produce 3.7x10(-7) molecules of singlet oxygen per chlorophyll molecule in a second when illuminated with the photosynthetic photon flux density of 2000molm(-2)s(-1).

  • 34. Kropacheva, Tatyana
    et al.
    Feikema, Onno
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Feyziyev, Yashar
    Styring, Stenbjörn
    Hoff, Arnold
    Quinone-induced high-spin state of cytochrome b559 in photosystem II2003In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 294, p. 471-482Article in journal (Refereed)
  • 35. Magnuson, Ann
    et al.
    Rova, Maria
    Mamedov, Fikret
    Fredriksson, Per-Olaf
    Styring, Stenbjörn
    The role of cytochrome b559 and tyrozineD in protection against photoinhibition during in vivo photoactivation of photosystem II1999In: Biochimica et Biophysica Acta - Bioenergetics, ISSN 0005-2728, E-ISSN 1879-2650, Vol. 1411, p. 180-191Article in journal (Refereed)
  • 36.
    Magnuson, Ann
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Rova, Maria
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Fredriksson, P.-O.
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Changes in the oxidation state of cytochrome b559 and tyrosine-D during in vivo photoactivation of photosystem II1998In: Photosynthesis: Mechanisms and Effects / [ed] Garab, G., Kluwer Academic Publishers, 1998, p. 1097-1100Conference paper (Refereed)
  • 37. Magnusson, Ann
    et al.
    Rova, Maria
    Mamedov, Fikret
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Fredriksson, P.-O.
    Styring, Stenbjörn
    Changes in the oxidation state of cytochrome b559 and tyrosine-D during in vivo photoactivation of photosystem II1998In: Photosynthesis: Mechanisms and Effects / [ed] Garab, G., Kluwer Academic Publishers, 1998, p. 1097-1100Conference paper (Refereed)
  • 38.
    Mamedov, Fikret
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    Danielsson, Ravi
    Gadjieva, Rena
    Albertsson, Per-Ake
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science.
    EPR characterization of photosystem II from different domains of the thylakoid membrane2008In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 47, no 12, p. 3883-3891Article in journal (Refereed)
    Abstract [en]

    We report electron paramagnetic resonance (EPR) studies on photosystem, 11 (PSII) from higher plants in five different domains of the thylakoid membrane prepared by sonication and two-phase partitioning. The domains studied were the grana core, the entire grana stack, the grana margins, the stroma lamellae and the purified stromal fraction, Y100. The electron transport properties of both donor and acceptor sides of PSII such as oxygen evolution, cofactors Y-D, Q(A), the CaMn4-cluster, and Cytb559 were investigated. The PSII content was estimated on the basis of oxidized YD and Q(A)(_) Fe2+ signal from the acceptor side vs Chl content (100% in the grana core fraction). It was found to be about 82% in the grana, 59% in the margins, 35% in the stroma and 15% in the Y100 fraction. The most active PSH centers were found in the granal fractions as was estimated from the rates of electron transfer and the S-2 State multiline EPR signal. In the margin and stromal fractions the multiline signal was smaller (40 and 33%, respectively). The S2 state multiline could not be induced in the Y100 fraction. In addition, the oxidized LP Cytb559 prevailed in the stromal fractions while the HP form dominated in the grana core. The margins and entire grana fractions have Cytb559 in both potential forms. These data together with previous analyses indicate that the sequence of activation of the PSII properties can be represented as: PSII content > oxygen evolution > reduced Cytb559 > dimerization of PSII centers in all fractions of the thylakoid membrane with the gradual increase from stromal fractions via margin to the grana core fraction. The results further support the existence of a PSII activity gradient which reflects lateral movement and photoactivation of PSII centers in the thylakoid membrane. The possible role of the PSII redox components in this process is discussed.

  • 39.
    Mamedov, Fikret
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Danielsson, Ravi
    Suorsa, Marjaana
    Paakkarinen, Virpi
    Aro, Eva-Mari
    Styring, Stenbjörn
    Super-complex organization of photosystem II in the different domains of the thylakoid membrane2005In: Photosynthesis: Fundamental Aspects to Global Perspective / [ed] van der Est A. and Bruce D., 2005, p. 255-256Conference paper (Refereed)
  • 40.
    Mamedov, Fikret
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Gadjieva, Rena
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Oxygen-induced changes in the redox state of the cytochrome b559 in photosystem II depend on the integrity of the Mn cluster2007In: Physiologia Plantarum: An International Journal for Plant Biology, ISSN 0031-9317, E-ISSN 1399-3054, Vol. 131, no 1, p. 41-49Article in journal (Refereed)
    Abstract [en]

    The effect of oxygen and anaerobiosis on the redox properties of Cyt b559 was investigated in PSII prepns. from spinach with different degree of disintegration of the donor side. Comparative studies were performed on intact PSII membranes and PSII membranes that were deprived of the 18-kDa peripheral subunit (0.25 NaCl washed), the 18- and 24-kDa peripheral subunits (1 M NaCl washed), the 18-, 24- and 33-kDa peripheral subunits (1.2 M CaCl2 washed), Cl depleted and after complete depletion of the Mn cluster (Tris washed). In active PSII centers, about 75% of Cyt b559 was found in the high-potential form and the rest in the intermediate potential form. With decompn. of the donor side, the intermediate potential form started to dominate, reaching more than 90% after Tris treatment. The oxygen-dependent conversion of the intermediate potential form of Cyt b559 into the low-potential and high-potential forms was only obsd. after treatments that directly affect the Mn cluster. In PSII membranes, deprived of all three extrinsic subunits (CaCl2 treatment), 21% of the intermediate potential form was converted into the low-potential form and 14% into the high-potential form by the removal of oxygen. In Tris-washed PSII membranes, completely lacking the Mn cluster, this conversion amounted to 60 and 33%, resp. In intact PSII membranes, the oxygen-dependent conversion did not occur. The possible physiol. role of this oxygen-dependent behavior of the Cyt b559 redox forms during the assembly/photoactivation cycle of PSII is discussed.

  • 41. Mamedov, Fikret
    et al.
    Gadjieva, R.M.
    Gasanov, R.A.
    About the mechanism of PSII reaction center D1 protein degradation1993In: Notes Azerb. Acad. Sci. Biol., no 4-6, p. 30-33Article in journal (Refereed)
  • 42. Mamedov, Fikret
    et al.
    Gasanov, R.A.
    Effect of removal of peripheral polypeptides on photoinhibition of oxygen evolving PSII particles from spinach1993In: Biochemistry (Moscow), Vol. 58, p. 809814-Article in journal (Refereed)
  • 43. Mamedov, Fikret
    et al.
    Gasanov, R.A.
    Effect of strong light on spinach photosystem II donor side reactions1995In: Photosynthesis: from light to biosphere / [ed] Mathis, P., 1995, p. 255-258Conference paper (Refereed)
  • 44. Mamedov, Fikret
    et al.
    Gasanov, R.A.
    Photoactivation of modified and reactivated photosystem II oxygen evolving particles1994In: Turkish J. of Botany, Vol. 18, p. 453-456Article in journal (Refereed)
  • 45.
    Mamedov, Fikret
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Havelius, Kajsa
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    ESEEM study of the light-inducible Split S1 EPR signal from photosystem II2008In: Photosynthesis. Energy from the Sun / [ed] Allen J.F., Gant E., Golbeck J.H. and Osmond B., Springer , 2008, p. 419-422Conference paper (Refereed)
  • 46.
    Mamedov, Fikret
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Nowaczyk, Marc M.
    Thapper, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Rögner, Matthias
    Styring, Stenbjörn
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Photochemistry and Molecular Science, Molecular Biomimetics.
    Functional characterization of monomeric photosystem II core preparations from Thermosynechococcus elongatus with or without the Psb27 protein2007In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 46, no 18, p. 5542-5551Article in journal (Refereed)
    Abstract [en]

    Two monomeric fractions of photosystem II (PS II) core pacticles from the thermophilic cyanobacterium Thermosynechococcus elongatus have been investigated using flash-induced variable fluorescence kinetics and EPR spectroscopy. One fraction was highly active in oxygen evolution and contained the extrinsic protein subunits PsbO, PsbU, and PsbV. The other monomeric fraction lacked oxygen evolving activity as well as the three extrinsic subunits, but the luminally located, extrinsic Psb27 lipoprotein was present. In the monomeric fraction with bound Psb27, flash-induced variable fluorescence showed an absence of oxidizable Mn on the donor side of PS II and impaired forward electron transfer from the primary quinone acceptor, QA. These results were confirmed with EPR spectroscopy by the absence of the \"split S1\" interaction signal from YZ.bul. and the CaMn4 cluster and by the absence of the S2-state multiline signal. A different protein compn. on the donor side of PS II monomers with Psb27 was also supported by the lack of an EPR signal from cytochrome c550 (in the PsbV subunit). In addn., we did not observe any oxidn. of cytochrome b559 at low temp. in this fraction. The presence of Psb27 and the absence of the CaMn4 cluster did not affect the protein matrix around YD or the acceptor side quinones as can be judged from the appearance of the corresponding EPR signals. The diminished electron transport capabilities on both the donor and the acceptor side of PS II when Psb27 is present give further indications that this PS II complex is involved in the earlier steps of the PS II repair cycle.

  • 47.
    Mamedov, Fikret
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Rintamäki, Eevi
    Aro, Eva-Mari
    Andersson, Bertil
    Styring, Stenbjörn
    Influence of protein phosphorylation on the electron transport properties of photosystem II2002In: Photosynthesis Research, ISSN 0166-8595, E-ISSN 1573-5079, Vol. 74, p. 61-72Article in journal (Refereed)
  • 48. Mamedov, Fikret
    et al.
    Sayre, T.R.
    Styring, Stenbjörn
    Involvement of histidine 190 on the D1 protein in electron/proton transfer reactions on the donor side of photosystem II1998In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 37, p. 11039-11045Article in journal (Refereed)
  • 49.
    Mamedov, Fikret
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström.
    Smith, Paul
    Styring, Stenbjörn
    Pace, Ron
    Relaxation behavior of the tyrosine YD radical in photosystem II: evidence for strong dipolar interaction with paramagnetic centers in the S1 and S2 States2004In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 6, p. 4890-4896Article in journal (Refereed)
  • 50. Mamedov, Fikret
    et al.
    Stefansson, Hreinn
    Albertsson, Per-Åke
    Styring, Stenbjörn
    Photosystem II in different parts of the thylakoid membrane: a functional comparison between different domains2000In: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 39, p. 10478-10486Article in journal (Refereed)
12 1 - 50 of 89
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf