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41Author    Kazuhiko Satoh, Yasuhiro Kashino, Hiroyuki KoikeRequires cookie*
 Title    Electron Transport from QA to Thymoquinone in a Synechococcus Oxygen-Evolving Photosystem II Preparation: Role of QB and Binding Affinity of Thymoquinone to the QB Site  
 Abstract    We have recently shown that binding affinities o f benzoquinones can be estimated by two methods in photosystem (PS) II particles (K. Satoh et al., Biochim. Biophys. Acta 1 1 0 2 ,4 5 -5 2 (1992)). U sing these methods we calculated the binding affinity o f thym oquinone (2-methyl-5-isopropyl-/?-benzoquinone) to the Q B site and studied how the quinone accepts electrons in oxygen-evolving PS II particles isolated from the thermophilic cyanobacteria, Synechococcus elongatus and S. vulcanus. The results are as follows: (1) The binding constant o f thym oqui­ none to the Q B site determined by several methods was around 0.33 m M . (2) At low thym oqui­ none concentrations the quinone was supposed to accept electrons via QB-plastoquinone, whereas at high concentrations the quinone seemed to bind to the QB site and accept an elec­ tron directly from Q~A. Lower rates o f photoreduction o f the quinone at high concentrations were attributed to a slower turnover rate o f the quinone at the QB site than that o f endogenous plastoquinone. (3) A model for the function o f plastoquinone at the Q B site, which can explain all the results, was presented. According to this model, the plastoquinone molecule at the Q B site is not replaced by another plastoquinone molecule. Instead, it transfers electrons to pool plastoquinone molecules by turning over its head group but remaining its long side chain bound to the PS II complexes. 
  Reference    Z. Naturforsch. 48c, 174 (1993); received November 9 1992 
  Published    1993 
  Keywords    Q b Site, Photosystem II, Thym oquinone, Plastoquinone, Synechococcus 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0174.pdf 
 Identifier    ZNC-1993-48c-0174 
 Volume    48 
42Author    Sophie Creuzet, TeresaM. Iranda, Jean-M Arc DucruetRequires cookie*
 Title    Comparison of Experimental and Calculated Hydrogen Bonding Properties of Some Urea and Triazine Inhibitors of Photosystem II  
 Abstract    Previous studies o f structure/activity relationships o f photosystem II inhibitors, including com parisons o f their inhibitory power in herbicide-resistant and susceptible chloroplasts, have led to predict the role o f hydrogen bonding, associated to hydrophobicity, in the binding onto the Qb site. The crystallographic structures o f bacterial reaction centers now allow these bonds to be identified. In order to be able to understand the binding o f various herbicides and the effects o f resistance mutations within the Q B site, a reliable estimation o f hydrogen bonding strengths is needed. We show here, by calculating interactions with model com pounds, con ­ trolled by physicochemical measurements, that the hydrogen bonding properties o f the C = X nucleophilic moiety present in most PS II inhibitors are different for triazines as compared to urea or amide derivatives. Semiempirical methods (AM 1) fail to reproduce the energies o f hy­ drogen bonds between a triazine ring nitrogen and a phenolic proton. An empirical method (SI BFA), designed to reproduce interaction energies, has been adapted with the aim o f calculat­ ing the binding energies o f various herbicides with models o f the Q B site. 
  Reference    Z. Naturforsch. 48c, 179 (1993); received November 12 1992 
  Published    1993 
  Keywords    Herbicide, Herbicide Resistance, Hydrogen Bonding, M olecular Calculation, Photosystem II 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0179.pdf 
 Identifier    ZNC-1993-48c-0179 
 Volume    48 
43Author    V. A. Boichenko, V. V. Klimovb, S. R. Mayes3, J. Barber1, T. Echnology, M. Edicine, London Sw, A. Y., U. K.Requires cookie*
 Title    Characterization of the Light-Induced Oxygen Gas Exchange from the IC 2 Deletion Mutant of Synechocystis PCC 6803 Lacking the Photosystem II 33 kDa Extrinsic Protein  
 Abstract    The absence o f the extrinsic M n-stabilizing 33 kD a protein in the IC 2 mutant o f Synecho­ cystis PCC 6803 disturbs the redox cycling o f the water splitting system and retards the formation o f its higher S-states (I. Vass, K.. We have performed analyses o f the flash-induced oxygen exchange in the mutated cyanobacterium to clarify further the role o f the 33 kD a protein. Under aerobic conditions, both the wild type and IC2 mutant show a relative­ ly slow signal o f oxygen rise on the first flash which is increased about twice by the addition o f 10 (aM D C M U and significantly diminished by lowering the oxygen concentration in the medi­ um. According to action spectra measurements, this m ode o f apparent oxygen release is me­ diated by PS I and can be attributed to a light induced inhibition o f respiratory activity. In contrast to the wild type, having the usual oxygen evolution flash pattern with a periodicity o f four, the IC2 mutant shows a binary oscillation pattern o f flash-induced respiratory oxygen exchange at a flash frequency 10 Hz, being dampened with D C M U or by a lower flash fre­ quency (< 1 Hz). Oxygen evolution due to water splitting is clearly seen in the IC2 mutant when background far-red illumination is applied to saturate the signal due to respiratory inhi­ bition, but a quadruple oscillatory com ponent o f flash-induced oxygen evolution appears only in the presence o f artificial electron acceptors under partial aerobic conditions. The mutant possesses a higher PS I/PS II ratio compared to the wild type, as judged from both the flash-induced yields and quantum efficiencies o f the steady-state rates o f the oxygen exchange reac­ tions. Estimates o f antenna sizes indicate about a 20% decrease o f optical cross-section at 675 nm o f the PS II unit in IC 2 mutants in comparison with the wild type. It is suggested that the absence o f the 33 kDa protein leads to a m odification o f the PS II assembly and because o f the slowing down o f the S-state cycle, the rate o f cyclic electron flow around PS II is enhanced. It seems that the absence o f the 33 kD a protein in Synechocystis 6803 also disturbs energy transfer between adjacent PS II core complexes and may also alter their association with the phycobilisomes. 
  Reference    Z. Naturforsch. 48c, 224—201 (1993); received December 10 1992 
  Published    1993 
  Keywords    Photosystem II, Oxygen Evolution, 33 kD a Protein, Synechocystis, Mutants 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0224.pdf 
 Identifier    ZNC-1993-48c-0224 
 Volume    48 
44Author    G. Renger, H. M. Gleiter, E. Haag, F. ReifarthRequires cookie*
 Title    Photosystem II: Thermodynamics and Kinetics of Electron Transport from Qa" to Q b(Q b' ) and Deleterious Effects of Copper(II)  
 Abstract    Studies on thermodynamics and kinetics o f electron transfer from QA~ to QB(QB") were per­ formed by m onitoring laser flash induced changes o f the relative fluorescence emission as a function o f temperature (220 K < T < 310 K) in isolated thylakoids and PS II membrane frag­ ments. In addition, effects o f bivalent metal ions on PS II were investigated by measuring conven­ tional fluorescence induction curves, oxygen evolution, manganese content and atrazine bind­ ing mostly in PS II membrane fragments. It was found: a) the normalized level o f the fluores­ cence remaining 10 s after the actinic flash (FJF0) steeply increases at temperatures below -1 0 to -2 0 °C, b) the fast phase o f the transient fluorescence change becomes markedly retard­ ed with decreasing temperatures, c) am ong different cations (Cu2+, Zn2+, Cd2+, N i2+, Co2+) only Cu2+ exhibits marked effects in the concentration range below 100 jim and d) Cu2+ decreases the normalized variable fluorescence, inhibits oxygen evolution and diminishes the affinity to atrazine binding without affecting the number o f binding sites. The content o f about four manganeses per functionally competent oxygen evolving complex is not changed by [Cu2+] < 70 |iM. Based on these findings it is concluded: i) a temperature dependent equilibrium between an inactive (I) and active (A) state o f QA~ reoxidation by Q b(Qb) is characterized by standard 
  Reference    Z. Naturforsch. 48c, 234 (1993); received November 23 1992 
  Published    1993 
  Keywords    Photosystem II, Q B-Site, Copper(II) Effects, Fluorescence, Oxygen Evolution 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0234.pdf 
 Identifier    ZNC-1993-48c-0234 
 Volume    48 
45Author    J. SymRequires cookie*
 Title    The Role of D 1* in Light-Induced D 1 Protein Turnover in Leaves  
 Abstract    ea, H arald R . B olh à r-N ord en kam pfb, and C hrista C ritch ley3 Light-induced degradation o f the D 1 protein of photosystem II (PS II) was determined by radioactive pulse-chase labelling experiments in intact leaves o f Schefflera polybotrya. PS II photochemical efficiency was monitored by measuring chlorophyll fluorescence. A significant and consistent decline in the F J F m ratio was taken to indicate photoinhibition. The formation and degradation o f a modified form o f the D 1 protein, D 1*, was different under photoinhibi-tory or non-photoinhibitory light conditions. At photoinhibitory irradiance greater amounts o f D 1 * were formed relative to D 1, and the degradation of D 1* was slower when compared with non-photoinhibitory irradiance. The formation and degradation o f D 1* were therefore shown to be at least partly light intensity dependent. Higher light intensities appeared to slow D 1* degradation, which suggests a modification in PS II turnover properties. 
  Reference    Z. Naturforsch. 48c, 246 (1993); received December 12 1992 
  Published    1993 
  Keywords    Photosynthesis, Photosystem II, Photoinhibition, D 1 Degradation, Chlorophyll Fluorescence 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0246.pdf 
 Identifier    ZNC-1993-48c-0246 
 Volume    48 
46Author    SimonP M Ackay, PatrickJ. O 'malleyRequires cookie*
 Title    Molecular Modelling of the Interactions between Optically Active Triazine Herbicides and Photosystem II  
 Abstract    The Q b binding site o f photosystem II in green plants displays stereoselectivity for the (S') stereoisomer o f the a-m ethylbenzyl derivative o f atrazine but not for derivatives with smaller substituents such as sec-butyl. We have shown that interactive models reflect the experimental data by determining the intermolecular energies between the D 1 protein binding region (resi­ dues Leu 210 to Val 280) and the triazine analogs. The intermolecular energy was calculated by van der W aals and electrostatic interactions after energy minimization o f the combined structures to reduce inter and intramolecular strain. On the basis o f these assumptions the role o f stereoselectivity for optically active triazines was site responsible such stereoselectivity was identified. 
  Reference    Z. Naturforsch. 48c, 474 (1993); received January 13/February 16 1993 
  Published    1993 
  Keywords    Atrazine, Electrostatic Interactions, Intermolecular Energy, Molecular M odelling, Photosystem II 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0474.pdf 
 Identifier    ZNC-1993-48c-0474 
 Volume    48 
47Author    E. B. Racht, A. TrebstRequires cookie*
 Title    Hypothesis on the Control of D 1 Protein Turnover by Nuclear Coded Proteins in Chlamydomonas reinhardtii  
 Abstract    A hypothesis is presented on the events in the degradation of the D 1 protein of photosys­ tem II in the light. It proposes the existence of a nuclear encoded cleavage system that is turning over and which is m odulated by its phosphorylation state. A new experimental ap­ proach is presented in which the D 1 protein degradation under photoinhibitory light is tested in Chlam ydom onas reinhardtii grown under phosphate deficiency and pretreated with cyclo-heximide. Under these conditions the degradation of the D 1 protein is delayed whereas in C hlam y­ dom onas reinhardtii grown in full medium the D 1 protein is rapidly disappearing in high light upon addition o f chloramphenicol (CAP) or lincomycin for inhibiting the resynthesis of the D 1 protein . Cycloheximide (C H I) has little effect on photoinhibition in such control cells. In cells grown, however, for 20 h in phosphate deficiency -such that there is not yet loss of photosynthesis capacity -pretreatment with cycloheximide or canavanine in low light the degradation of the D 1 protein even in 6 h high light is prevented to an appreciable extent. Further addition of CAP or lincomycin has only a small effect. [14C]leucine incorporation was used to show that there is no resynthesis and that the presence of the D 1 protein is due to a delay of degradation. The results are interpreted to show that excess high light which converts the D 1 protein into a potentially, degradable m ode is not sufficient for degradation of the D 1 protein. A cleavage system is needed as well. It is postulated that under phosphate deficiency and pre­ treatment with CHI or canavanine a nuclear coded cleavage system for the D 1 protein is depleted, i.e. the cleavage system for the rapidly turning over D 1 is also turning over. It is shown that under phosphate deficiency an alkaline phosphatase activity in the chloro­ plast and the thylakoid membrane o f Chlam ydom onas reinhardtii is increased. It is proposed that the ratio of kinase/phosphatase converts an active, stable phosphorylated cleavage system into a labile unphosphorylated and turning over state. 
  Reference    Z. Naturforsch. 49c, 439 (1994); received January 31/May 13 1994 
  Published    1994 
  Keywords    Chlamydomonas, D 1 Protein, Photoinhibition, Photosystem II, Phosphate Deficiency 
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 TEI-XML for    default:Reihe_C/49/ZNC-1994-49c-0439.pdf 
 Identifier    ZNC-1994-49c-0439 
 Volume    49 
48Author    Achim TrebstRequires cookie*
 Title    The Topology of the Plastoquinone and Herbicide Binding Peptides of Photosystem II in the Thylakoid Membrane  
 Abstract    The 32 kDa herbicide and O b binding peptide (D-l protein) and its homologous 34 kDa peptide (D-2 protein) are integral membrane subunits of photosystem II. A model for their folding through the thylakoid membrane in five transmembrane a-helices is proposed from the compari­ son of amino acid sequence and hydropathy index plot homologies with subunits of the bacterial system. Following recent data on the X-ray structure of a bacterial photosystem the binding niche for O b is interpreted on the basis of the amino acid changes found in the 32 kDa peptide in herbicide tolerant higher plants and algae. 
  Reference    Z. Naturforsch. 41c, 240—245 (1986); received November 25 1985 
  Published    1986 
  Keywords    birthday Plastoquinone, Herbicide Binding Protein Membrane Proteins, Photosystem II, Thylakoid Membrane 
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 TEI-XML for    default:Reihe_C/41/ZNC-1986-41c-0240.pdf 
 Identifier    ZNC-1986-41c-0240 
 Volume    41 
49Author    Gudrun Wälzlein, AchimE. Gau, ElfriedeK. PistoriusRequires cookie*
 Title    Further Investigations about the Flavin in the L-Amino Acid Oxidase and a Possible Flavin in Photosystem II Complexes from the Cyanobacterium Anacystis nidulans  
 Abstract    The absorption spectrum of the previously purified L-amino acid oxidase from the cyanobac-terium Anacystis nidulans has shown considerable variation with each preparation and the spec-trum in several preparations was quite different from the absorption spectrum of other simple flavoproteins (E. K. Pistorius and A. E. Gau, Biochim. Biophys. Acta 849, 203, 1986). Here we show that the spectral complexity and variability of the L-amino acid oxidase can be largely explained by the presence of a modified flavin derivative of yet unknown structure besides oxidized FAD and FAD semiquinone. After removal from the enzyme this modified chromophore has absorption maxima at 260, 396 and in the 600 nm region. This derivative of FAD seems to be formed in variable amounts during the purification of the enzyme. On the other hand, extraction of Anacystis photosystem II complexes which contain the flavoprotein, almost exclusively yields modified flavin derivatives and practically no authentic oxidized FAD. The spectrum of the chromophores which have been extracted from photosystem II complexes at different purification stages, is either similar (although not identical) to the spectrum of the chromophore extracted from the isolated L-amino acid oxidase or similar to the spectrum of reduced flavin. All extracted chromophores show a fluorescence emission in the 420 to 560 nm region when excited with light of 390 nm. These results indicate that the flavin present in the L-amino acid oxidase protein as well as in photosystem II complexes from A. nidulans rapidly undergoes modification reactions of yet unknown nature to yield several closely related FAD derivatives. This might possibly be the reason why so far no flavin has been detected in photosys-tem II. The presence of such modified flavin derivatives in photosystem II complexes of A. nidulans as shown here is an additional support of our hypothesis that an unusual flavin is functional on the donor side of photosystem II. 
  Reference    Z. Naturforsch. 43c, 545—553 (1988); received January 25 1988 
  Published    1988 
  Keywords    L-Amino Acid Oxidase, Flavoprotein, Photosystem II, Cyanobacteria, Anacystis nidulans 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0545.pdf 
 Identifier    ZNC-1988-43c-0545 
 Volume    43 
50Author    AchimE. Gau, Gudrun Wälzlein, Susanne Gärtner, Matthias Kuhlmann, Susanne Specht, ElfriedeK. PistoriusRequires cookie*
 Title    Immunological Identification of Polypeptides in Photosystem II Complexes from the Cyanobacterium Anacystis nidulans  
 Abstract    Photosystem II complexes from the cyanobacterium Anacystis nidulans have been investigated by Western blots with antisera raised against four photosystem II peptides from plants and with an antiserum raised against the soluble L-amino acid oxidase protein from/1. nidulans to achieve an iden­ tification of the polypeptides — especially of the L-amino acid oxidase related protein — in isolated photosystem II complexes. Anacystis photosystem II complexes which were solubilized with lauryldimethylamine N-oxide and purified by sucrose cushion and sucrose gradient centrifugation, contained as major Coomassie brilliant blue stained polypeptides a 71 kDa band of unknown identity, a 62 kDa band, which partly contained D-l, a 55 and 49 kDa band which were immuno-reactive with an antiserum to the 47 kDa peptide of tobacco PS II complexes, and three distinct bands in the 30 kDa region. These latter bands could be identified as the extrinsic Mn stabilizing peptide (27—30 kDa), D-l (30—33 kDa) and a 36 kDa peptide (35 — 38 kDa) which crossreacted with the antiserum raised against the soluble L-amino acid oxidase protein of 50 kDa. These results suggest that the 36 kDa peptide present in purified photosystem II complexes from A. nidulans might be a processed form of the soluble 50 kDa L-amino acid oxidase protein. 
  Reference    Z. Naturforsch. 44c, 971—975 (1989); received June 22 1989 
  Published    1989 
  Keywords    Photosystem II, L-Amino Acid Oxidase, Antibody, Cyanobacteria, Anacystis nidulans 
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 TEI-XML for    default:Reihe_C/44/ZNC-1989-44c-0971.pdf 
 Identifier    ZNC-1989-44c-0971 
 Volume    44 
51Author    G. Ajlani, I. Meyer, C. Astier, C. VernotteRequires cookie*
 Title    Inhibition of Photosystem II by Ioxynil in Wild Type and Resistant Mutant of Synechocystis 6714  
 Abstract    A Synechocystis 6714 mutant resistant to the phenol-type herbicide ioxynil was isolated and characterized. Ioxynil was shown to inhibit both the donor and the acceptor sides of photosystem II, but at different concentrations. The mutation found in the psbA gene (encoding the D, protein) at codon 266 (asparagine to threonine) [G. Ajlani, I. Meyer, C. Vernotte, and C. Astier, FEBS Lett. 246, 207—210 (1989)] gives a ten-fold resistance of the acceptor side to ioxynil without any modification of the sensitivity of the donor side. Electron transfer between the primary and the secondary acceptor of photosystem II was identical in the mutant and the wild type. The mutant remains sensitive to atrazine and is even more sensitive to D C M U than the wild type. 
  Reference    Z. Naturforsch. 44c, 979 (1989); received June 16 1989 
  Published    1989 
  Keywords    Phenolic Herbicide, Ioxynil, Photosystem II, Cyanobacteria, D i Protein 
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 Identifier    ZNC-1989-44c-0979 
 Volume    44 
52Author    HelenG M Cfadden, JohnN. PhillipsRequires cookie*
 Title    Synthesis and Use of Radiolabelled Cyanoacrylate Probes of the Photosystem II Herbicide Binding Site  
 Abstract    Cyanoacrylates are potent inhibitors o f photosynthetic electron transport (PET) and are po­ tentially useful probes o f the photosystem II herbicide binding site. A series o f cyanoacrylates was synthesized and the Hill inhibition activities evaluated in order to select com pounds suita­ ble for radioactive synthesis. A cyanoacrylate, 2-(2-nitrophenoxy)ethyl 3-benzylamino-2-cyano-2-pentenoate, was found to displace diuron from the photosystem II herbicide binding site. For this compound the dissociation constant o f the inhibitor/binding site complex was found to be 2 x 10"8 M with an active site concentration o f 2 nm ol/m g chlorophyll. In a similar system the corresponding figures for diuron were 1.2 x 10"8 m and 1.3 nm ol/m g chlorophyll. Photoaffinity labelling o f 1% II thylakoid proteins with 2-(2-azidophenoxy)ethyl 3-[7-l4C]-benzylam ino-2-cyano-2-pentenoate showed weak binding in the 32 and 28 kD mass regions, consistent with binding to the D, peptide. 
  Reference    Z. Naturforsch. 45c, 196—202 (1990); received September 20/N ovem ber 10 1989 
  Published    1990 
  Keywords    Cyanoacrylate, Photoaffinity Labelling, Photosystem II, Com petitive Inhibition, Diuron 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0196.pdf 
 Identifier    ZNC-1990-45c-0196 
 Volume    45 
53Author    J.Dirk Naber, JackJ S Van RensenRequires cookie*
 Title    Activity of Photosystem II Herbicides Is Related with Their Residence Times at the D 1 Protein  
 Abstract    The reversible binding kinetics o f atrazine, diuron and ioxynil were measured via their bind­ ing and release parameters during steady state inhibition o f electron transport. The parameters were determined in isolated chloroplasts o f peas and o f triazine-resistant and -susceptible bio­ types o f Chenopodium album using a kinetic model. This model is based on the flash-induced oxygen evolution patterns o f isolated broken chloroplasts. It was found that the binding parameters were always significantly higher in the case o f an oxidized acceptor quinone complex as compared with a semi-reduced complex. Triazine resist­ ance seems to originate from a significant increase o f the release kinetics. The release parame­ ters could be used to calculate the residence times o f the herbicides at the D 1 protein. The values o f these residence times were always much higher for the herbicides than for Q B; this explains the inhibition o f electron transport. The only exception was the residence time o f atra­ zine in the resistant biotype, where the value was close to that o f Q B. It is concluded that the "on" kinetics o f a com pound to its binding environment at the D 1 protein are determined principally by the accessibility o f the niche to the com pound. The dif­ ferences in activity between herbicides are mainly due to variations in the release kinetics. 
  Reference    Z. Naturforsch. 46c, 575—5 (1991); received March 18 1991 
  Published    1991 
  Keywords    Chloroplasts, Photosystem II, D 1 Protein, Herbicides, Triazine Resistance 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0575.pdf 
 Identifier    ZNC-1991-46c-0575 
 Volume    46 
54Author    P. He, K. P. Bader, G. H. Schm, G. Renger, K. P. Bader, G. H. SchmidRequires cookie*
 Title    Mass Spectrometric Analysis of N 2-Formation Induced by the Oxidation of Hydrazine and Hydroxylamine in Flash Illuminated Thylakoid Preparations of the Filamentous Cyanobacterium Oscillatoria chalybea  
 Abstract    Analogue In tobacco chloroplasts hydrazine-dependent dinitrogen form ation measured by mass spec­ trometry as the consequence o f short saturating light flashes is always linked to a substantial oxygen uptake (1990). However, in thylakoids o f the filamentous cyanobacterium Oscillatoria chalybea this dinitrogen formation is not linked to an apparent 0 2-uptake, even at the high concentration o f 1 mM hydrazine. Whereas in tobacco chloroplasts Tris-treatment does not affect hydrazine de­ pendent dinitrogen formation up to a concentration o f 3 mM hydrazine, Tris-treatment o f thy­ lakoids o f O. chalybea affects strongly both oxygen evolution and dinitrogen evolution under a single turnover flash as well as under ten flashes. In contrast to tobacco chloroplasts, the pres­ ence o f hydrazine up to concentrations o f 3 mM does not substantially affect photosynthetic 0-,-evolution. The observed dinitrogen evolution is affected by D C M U regardless whether in­ duced by a single turnover flash or by ten flashes, whereas in tobacco dinitrogen evolution and the 0-,-uptake linked to it (which is not observed in the cyanobacterium) were clearly not af­ fected by D C M U in the single turnover flash. In Oscillatoria the earlier described Photosystem II-mediated H-,0-, formation and decom position is influenced by hydrazine. In the presence o f 300 hm hydrazine the usually present 0 2-uptake leading to H:0 : formation appears dimin­ ished. 
  Reference    Z. Naturforsch. 46c, 629 (1991); received March 21 1991 
  Published    1991 
  Keywords    Filamentous Cyanobacterium, Photosystem II, Water Splitting, S-States, Hydrogen-Peroxide 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0629.pdf 
 Identifier    ZNC-1991-46c-0629 
 Volume    46 
55Author    ChunheX. Ua, Yong Zhub, GovindjeeacRequires cookie*
 Title    Differential Inhibition and Rephasing of Photosystem II Electron Acceptor Side by Monohalogenated Acetates of Different Hydrophobicity  
 Abstract    We demonstrate here that monohalogenated acetates (M F A , m onofluoroacetate; M CA, m onochloroacetate; M BA, monobrom oacetate) are unique probes o f the electron acceptor side o f the photosystem II (PS II) reaction center: (1) they differentially inhibit the reoxidation o f the reduced primary plastoquinone electron acceptor, QA~, by the secondary plastoquinone electron acceptor QB, and increase the equilibrium [QA_] in the order: M BA > M C A > M FA; and (2) M CA and M BA rephase the PS II electron acceptor side, a rather unusual effect. This results in flash number dependence o f [QA_] with maxima at even flashes to change to odd flashes. Furthermore, we demonstrate a correlation between the inhibitory activity o f the halo-genated acetates with their hydrophobicity (i.e., partition coefficient). 
  Reference    Z. Naturforsch. 47c, 711—7 (1992); received June 2 1992 
  Published    1992 
  Keywords    M onohalogenated Acetates, Photosystem II, Two Electron Gate, Hydrophobicity, Bicarbonate Effect 
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 TEI-XML for    default:Reihe_C/47/ZNC-1992-47c-0711.pdf 
 Identifier    ZNC-1992-47c-0711 
 Volume    47 
56Author    W.I G Ruszeckia, K. Strzałk, K.P B Ad Erc, A. R. Adunzc, G. H. SchmRequires cookie*
 Title    Involvement of the Xanthophyll Cycle in Regulation of Cyclic Electron Flow around Photosystem II  
 Abstract    In our previous study (Gruszecki et al., 1995) we have postulated that the mechanism of cyclic electron transport around photosystem II, active under overexcitation of the photosyn­ thetic apparatus by light is under control of the xanthophyll cycle. The combination of dif­ ferent light quality and thylakoids having various levels o f xanthophyll cycle pigments were applied to support this hypothesis. In the present work photosynthetic oxygen evolution from isolated tobacco chloroplasts was measured by means o f mass spectrometry under conditions of high or low levels of violaxanthin, being transformed to zeaxanthin during dark incubation in an ascorbate containing buffer at pH 5.7. Analysis of oxygen evolution and o f light-induced oxygen uptake indicate that the de-epoxidation o f violaxanthin to zeaxanthin results in an increased cyclic electron transport around PS II, thus dimishing the vectorial electron flow from water. An effect similar to de-epoxidation was observed after incubation of thylakoid membranes with specific antibodies against violaxanthin. 
  Reference    Z. Naturforsch. 51c, 47 (1996); received September 22/O ctober 18 1995 
  Published    1996 
  Keywords    Xanthophyll Cycle, Cyclic Electron Flow, Photosystem II, Oxygen Evolution, Blue Light Effect, Mass Spectrometry 
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 TEI-XML for    default:Reihe_C/51/ZNC-1996-51c-0047.pdf 
 Identifier    ZNC-1996-51c-0047 
 Volume    51 
57Author    Marie-Jose DelrieuRequires cookie*
 Title    Evidence for Unequal M isses in Oxygen Flash Yield Sequence in Photosynthesis  
 Abstract    The numerical analysis of the oxygen flash yield Yn sequences, alone, does not allow to choose between two models: equal S state misses with non negligible double hits or unequal misses with nearly no double hits. Nevertheless, the com parison o f the sequences in different conditions shows that the equal miss model is unrealistic: in very different experimental conditions (non saturating flash, different batch o f Chlorella or chloroplasts), a parallel variation of the hom o­ geneous miss and double hit factors is observed. This correlation seems strange within the equal miss model: misses come from incomplete reaction (i.e. for exemple insufficient light) and double hits i.e. double advancem ent come, in principle, from excessive light or too long flash; for these reasons, opposite variation of misses and double hits as a function of light intensity are ex­ pected. W ithin the equal miss model the inverse is exactly observed: at low flash light intensity (11%) which increases the misses, 16% of double hits are needed, which is quite unrealistic. In contrast, the unequal miss model explains such result quite naturally by a m athem atical property: any theoretical sequence with only a unique S state miss and no double hit can be fitted with homogeneous misses and double hits, which increase in parallel as a function o f the damping. Evidence for unequal misses in oxygen flash yield sequence is provided by the heterogeneous properties of the light saturation curves (M. J. D elrieu, Biochim. Biophys. Acta 592, 4 7 8 -4 9 4 (1980)). At high flash intensity, all, excepted the transition S ' 2 -*■ S3 , are saturated; the transition £ 2 -* S3 is far from saturation and its very large saturating light intensity is actually not known. A comparative study, in the same chloroplast batch, o f the oxygen yield patterns with attenuated flashes and of the experimental saturation curves of S states shows that only photo­ chemical misses (due to non saturation) exist. At high intensity, there is only a unique miss for the transition S 2 S 3 i.e. the probability for this transition is low. A model involving a second acceptor could explain the slow increase of transition probability o f S ' 2 -* S3 at high flash intensity. 
  Reference    Z. Naturforsch. 38c, 247—258 (1983); received N ovem ber 16 1982 
  Published    1983 
  Keywords    Oxygen Evolution, Photosystem II, M atrix Analysis, N on Saturating Flash Sequence, Electron Acceptor 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0247.pdf 
 Identifier    ZNC-1983-38c-0247 
 Volume    38 
58Author    W. I. Gruszecki3, K. Strzałkab, A. R. Adunzc, J. K. Rukb, G. H. SchmidcRequires cookie*
 Title    Blue Light-Enhanced Photosynthetic Oxygen Evolution from Liposome-Bound Photosystem II Particles; Possible Role of the Xanthophyll Cycle in the Regulation of Cyclic Electron Flow Around Photosystem II?  
 Abstract    Light-driven electron transport in liposom e-bound photosystem II (PS-II) particles be­ tween water and ferricyanide was monitored by bare platinum electrode oxymetry. The m odi­ fication of the experimental system with the exogenous quinones a-tocopherol quinone (a-TQ) or plastoquinone (PQ) resulted in a pronounced effect on photosynthetic oxygen evolution. The presence o f a-tocopherolquinone (a-T Q) in PS-II samples decreased the rate of red light-induced oxygen evolution but increased the rate o f green light-induced oxygen evolution. Blue light applied to the assay system in which oxygen evolution was saturated by red light resulted in a further increase o f the oxygen signal. These findings are interpreted in terms of a cyclic electron transport around PS-II, regulated by an excitation state of ß-carotene in the reaction centre of PS-II. A mechanism is postulated according to which energetic coupling of ß-carotene in the reaction centre of PS-II and that o f other antenna carotenoid pigments is regulated by the portion of the xanthophyll violaxanthin, which is under control of the xanthophyll cycle. 
  Reference    Z. Naturforsch. 50c, 61—6 (1995); received June 15/November 11 1994 
  Published    1995 
  Keywords    a-Tocopherol Quinone, Plastoquinone-9, Oxygen Evolution, Photosystem II, Cyclic Electron Transport, Xanthophyll Cycle 
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 TEI-XML for    default:Reihe_C/50/ZNC-1995-50c-0061.pdf 
 Identifier    ZNC-1995-50c-0061 
 Volume    50 
59Author    M. Tevini, K. PfisterRequires cookie*
 Title    Inhibition of Photosystem II by UV-B-Radiation  
 Abstract    The effect o f UV-B-radiation on PSII activity o f spinach chloroplasts was analyzed by m ea­ suring the integrity o f the herbicide-binding protein (H BP 32), by m easurem ent o f fluorescence induction in the presence o f Diuron (D C M U), and by m athem atical analysis o f the fluorescence induction curves. It was shown that UV-B inactivates the PSII a-centers but not PSII ^-centers. However, the possibility cannot be excluded that in add ition the donor site o f PSII near the reaction center is attacked by UV-B-radiation. 
  Reference    Z. Naturforsch. 40c, 129—133 (1985); received N ovem ber 7 1984 
  Published    1985 
  Keywords    Photosystem II, Variable Fluorescence, R eaction Centers, Spinach Chloroplasts, U V -B-R adiation 
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 TEI-XML for    default:Reihe_C/40/ZNC-1985-40c-0129.pdf 
 Identifier    ZNC-1985-40c-0129 
 Volume    40 
60Author    Joseph Hirschberg, NirO. Had, Iris Pecker, Ana RahatRequires cookie*
 Title    Isolation and Characterization of Herbicide Resistant Mutants in the Cyanobacterium Synechococcus R2  
 Abstract    Departm ent o f G en etics, The H ebrew University o f Jerusalem. Jerusalem. A variety of mutants which are resistant to triazine — and urea — classes of herbicides have been isolated in the cyanobacterium Synechococcus R 2. A ll the mutants that have been analyzed, show som e cross-resistance to different herbicides suggesting that these herbicides share a com m on binding site in photosystem II. Three psbA genes have been identified in Synechococcus R 2. The /« M -c o p y I gene was cloned from three mutants and used in D N A -m ed iated genetic transformation. It was found that in all three mutants this gene could transfer the mutation for herbicide resistance indicating that this gene codes for the herbicide resistant protein. 
  Reference    Z. Naturforsch. 42c, 758—7 (1987); received January 7 1987 
  Published    1987 
  Keywords    H erbicide Resistance, psb A G en e, Photosystem II, Cyanobacteria, Mutants 
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 TEI-XML for    default:Reihe_C/42/ZNC-1987-42c-0758.pdf 
 Identifier    ZNC-1987-42c-0758 
 Volume    42 
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