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'Photosystem II' in keywords Facet   Publication Year 1984  [X]
Facet   section ZfN Section C  [X]
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1984[X]
1Author    W. Im, F. J. Vermaas, G. Ern O, R. Enger, J. A. Arles, RntzenRequires cookie*
 Title    Herbicide/Quinone Binding Interactions in Photosystem II  
 Abstract    Many inhibitors prevent the oxidation o f the primary electron-accepting quinone (Q A) by the secondary quinone (Q B) in photosystem II by displacem ent o f Q B from its binding site. On the other hand, plastoquinone-1 and 6-azido-5-decyl-2,3-dim ethoxy-/?-benzoquinone displace herbicides. Binding studies show the herbicide/quinone interaction to be (apparently) competitive. The herbicide binding is influenced differentially by various treatments. In this paper it is shown that the affinity of, for example, brom oxynil is decreased by thylakoid unstacking or by light-or reductant-induced reduction o f certain thylakoid com ponents, whereas atrazine affinity remains unchanged. Furthermore, absence o f H C O j in the presence o f form ate leads to an affinity decrease o f bromoxynil and atrazine, but to an increase in i-dinoseb affinity. Other differential photosystem II herbicide effects are known from the literature. Since different and unrelated groups o f Q A oxidation inhibitors have been found, and because o f the above-mentioned dissim ilarities in binding characteristics for different inhibitor groups, the hypothesis o f non-identical, but "overlapping" binding sites for different herbicide groups and the native quinone must be more extensively defined. In this m anuscript we evaluate both the competitive herbicide/quinone binding m odel, and a m odel in which binding o f one ligand alters the protein conformation resulting in a dram atic decrease in the binding affinity o f ligands from other chemical groups; in this model ligands from the sam e or related chem ical groups bind competitively. Thus, the latter model proposes that only one herbicide or quinone m olecule can be bound with high affinity to the herbicide/quinone binding environm ent, but it depends on the chemical structure o f the ligands whether the binding interaction betw een two ligands is truly competitive or more indirect (allosteric), m ediated through the protein conform ation. 
  Reference    Z. Naturforsch. 39c, 368 (1984); received D ecem ber 1 1983 
  Published    1984 
  Keywords    Herbicide, Photosystem II, Plastoquinone, Photosynthesis, A llosteric interaction 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0368.pdf 
 Identifier    ZNC-1984-39c-0368 
 Volume    39 
2Author    D. Anny, J. Blubaugh, G. OvindjeeRequires cookie*
 Title    Comparison of Bicarbonate Effects on the Variable Chlorophyll a Fluorescence of C 0 2-Depleted and Non-C02-Depleted Thylakoids in the Presence of Diuron  
 Abstract    Evidence is presented from chlorophyll a fluorescence transient data for two sites o f bicar­ bonate (H C O j*) action in photosystem II. Both the absence o f H C O j (H C O j-depleted thyla­ koids) and a high concentration o f H C O j (60 m M H C O j added to non-depleted thylakoids) accelerate the variable chlorophyll a fluorescence rise in the presence o f 10 |i m diuron (D C M U). In non-HCOj-depleted thylakoids the effect is independent o f the order in which H C O j and DCM U are added, whereas in H CO J-depleted thylakoids, the effect is seen only when H C O j is added before DCM U. We propose that the effect seen in H C O j-depleted thylakoids is indirectly due to the binding o f H C O j functionally near the site o f D C M U binding, which is also where H CO j exerts its major effect on electron transport between the primary quinone QA and the plasto-quinone pool. We suggest that the smaller effect seen in non-HCOj-depleted thylakoids is due to the binding of HCOj at a second, lower affinity site. Binding at this site appears to require light, in con­ trast to the higher affinity site, which is inhibited by light. Bathocuproine, an inhibitor o f the H20 -to-silicomolybdate partial reaction, is synergistic with H C O j in its effect on the variable chlorophyll a fluorescence o f non-H C O j-depleted thylakoids, and may bind heterotropically with H CO j. Thus, this second site o f H C O j binding appears to be functionally near the batho­ cuproine binding site. 
  Reference    Z. Naturforsch. 39c, 378 (1984); received N ovem ber 14 1983 
  Published    1984 
  Keywords    Bicarbonate Effect, Chlorophyll Fluorescence, Photosystem II, Diuron, Bathocuproine 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0378.pdf 
 Identifier    ZNC-1984-39c-0378 
 Volume    39 
3Author    HowardH R Obinson, JulianJ E Aton-R, Ye, JackJ S Van, R. Ensen, G. OvindjeeRequires cookie*
 Title    The Effects of Bicarbonate Depletion and Formate Incubation on the Kinetics of Oxidation-Reduction Reactions of the Photosystem II Quinone Acceptor Complex  
 Abstract    Chloroplast thylakoid membranes depleted o f bicarbonate exhibit a slowed oxidation o f the primary quinone acceptor (QA) by the secondary quinone acceptor (Q B) o f photosystem II. The kinetics o f these slowed reactions have been follow ed by using short xenon flashes o f light both to excite photosystem II and to probe the redox state o f Q A. Thylakoids incubated with formate but not depleted o f bicarbonate showed the sam e pattern o f slowed reaction kinetics o f the quinone acceptors as seen in bicarbonate-depleted thylakoids. This led us to conclude that there was a simple com petition between bicarbonate and formate at this site; however, steady-state electron transfer measured with an oxygen electrode showed that although the bicarbonate-depleted thylakoids were indeed inhibited, rates in the form ate-incubated thylakoids were only slightly slowed. We suggest that the inhibition seen at the quinone acceptor site o f photosystem II depends in a subtle way upon the rate o f exchange o f bicarbonate and formate at this site. 
  Reference    Z. Naturforsch. 39c, 382 (1984); received N ovem ber 14 1983 
  Published    1984 
  Keywords    Chloroplasts, Photosystem II, Bicarbonate, Formate, Plastoquinone 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0382.pdf 
 Identifier    ZNC-1984-39c-0382 
 Volume    39 
4Author    A. Trebst, W. D. Onner, W. D. RaberRequires cookie*
 Title    Structure Activity Correlation of Herbicides Affecting Plastoquinone Reduction by Photosystem II: Electron Density Distribution in Inhibitors and Plastoquinone Species  
 Abstract    Molecular orbital calculations o f the net charge and the n charge distribution in several inhibitors and herbicides o f the functionally related group o f the diuron and dinoseb type are reported. They confirm the m odel that urea, am inotriazinone and triazine herbicides all have in common a positive ^-charge at a particular atom considered to be essential for binding. Phenol type inhibitors have different charge distribution and a m odel for their essential features is presented. The calculations support the finding that two different subunits with different binding characteristics are involved in inhibitor and plastoquinone function on the acceptor side o f photosystem II. Force-field model building and MO calculations o f the charge distribution o f a plastoquinone analogue with a butenyl side chain, o f two o f its sem iquinone forms and o f the hydroquinone, are reported, as well as their conform ation with the lowest energy content and their likely anionic forms. 
  Reference    Z. Naturforsch. 39c, 405—411 (1984); received D ecem ber 23 1983 
  Published    1984 
  Keywords    Herbicides, Plastoquinone, MO Calculation, Photosystem II 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0405.pdf 
 Identifier    ZNC-1984-39c-0405 
 Volume    39 
5Author    E. K. Pistorius, G. H. SchmidRequires cookie*
 Title    Studies on the O2 Evolution under Flash Light Illumination in Preparations of A nacystis nidulans  
 Abstract    The 0 2 yield under flash light illum ination in preparations o f Anacystis nidulans was exam ined in the presence o f redox components such as ferricyanide and ferrocyanide. W hen ferricyanide (1 mM) was added to the lyophilized, lysozym e treated and ED TA w ashed cells o f A. nidulans the familiar Joliot-Kok oscillalion with m axim um on the third flash and periodicity o f four was observed (in the presence o f added CaCl2 and M nCl2). H owever, when the ferricyanide con­ centration was increased to about 8 m M , a reduction o f the 0 2 evolution under flash illum ination was observed, and an 0 2 uptake could clearly be seen under the First and second flash. This 0 2 uptake was inhibited by D C M U and o-phenanthroline, but was not influenced by KCN or salicylhydroxamic acid. As ferrocyanide was progressively added to 1 m M ferricyanide, the oscillations faded out and the steady-state 0 2 evolution decreased. Light would progressively increase the 0 2 evolution and reduce the dam ping o f the oscillations. Two patterns o f 0 2 evolution under short saturating light flashes were observed with these Anacystis preparations on first illum ination in the presence o f cations but in the absence o f ferri­ cyanide. One pattern corresponded to the typical pattern w hich has been repeatedly described in the literature, but the second pattern gave the indication o f an initial "over-reduced" state o f the photosystem II reaction center. W ith suitable procedures the two patterns were interchangeable. Moreover, the effect o f L-arginine on the flash pattern was exam ined. The results are discussed in connection with the possible dual function o f the previously described flavin protein as an L-amino acid oxidase and as a com ponent o f the 0 2 evolving reaction center (E. K. Pistorius and H. Voss, Eur. J. Biochemistry 1 2 6 ,2 0 3 -2 0 9 (1982)). 
  Reference    Z. Naturforsch. 39c, 1097—1103 (1984); received August 20 1984 
  Published    1984 
  Keywords    0 2 Evolution, Photosystem II, Cyanobacteria, A nacystis nidulans 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-1097.pdf 
 Identifier    ZNC-1984-39c-1097 
 Volume    39 
6Author    M. D. Arie-Jose, ElrieuRequires cookie*
 Title    The Effects of 3-(3,4-Dichlorophenyl)-l,l-dimethylurea on the Photosynthetic Oxygen Complex  
 Abstract    In the presence o f trypsin and ferricyanide as external electron acceptor, lettuce chloroplasts are resistant to DCM U, showing that the inhibitory site o f D C M U is only situated on the accep­ tor side o f photosystem II. However, kinetic properties o f the oxygen evolving com plex are m od i­ fied at non-saturating concentrations o f D C M U . These changes are interpreted in terms o f a model with two distinct charges separation systems on the sam e center: the auxiliary donor-acceptor system D Q L implicated in the transitions S| -» • S 2 and S2 -*■ S 3 would be m uch less affected by DCM U than the main donor-acceptor system Y Q H after the first flash. 
  Reference    Z. Naturforsch. 39c, 347—350 (1984); received N ovem ber 28 1983 
  Published    1984 
  Keywords    Herbicides, Oxygen Evolution, Photosystem II, Electron Acceptors, Electron D onors 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0347.pdf 
 Identifier    ZNC-1984-39c-0347 
 Volume    39 
7Author    J.M D Ucruet, P. G. Aillard, J. V. IenotRequires cookie*
 Title    Use of Chlorophyll Fluorescence Induction Kinetics to Study Translocation and Detoxication of DCMU-Type Herbicides in Plant Leaves  
 Abstract    Transient levels o f the fluorescence induction rise were used to quantify partial photosynthesis inhibition by DC M U -type herbicides in w hole leaves. Assays in different crop or weed species showed a good accuracy in measurements (generally, variation was lower than 5%). This technique was applied to the problem o f varietal selectivity o f wheat towards chlortoluron. 
  Reference    Z. Naturforsch. 39c, 354 (1984); received N ovem ber 15 1983 
  Published    1984 
  Keywords    Chlorophyll Fluorescence, Photosystem II, H erbicides Translocation, D etoxication 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0354.pdf 
 Identifier    ZNC-1984-39c-0354 
 Volume    39 
8Author    Z. NaturforschRequires cookie*
 Title    Redox-State Dependent Changes of Inhibitor-Binding to the Photosystem II Acceptor Complex  
 Abstract    Binding o f radioactively labelled D C M U , ioxynil and terbutryn to spinach chloroplasts is determined following preillum ination by single-turnover, saturating light flashes. W ith all o f the three herbicides binary oscillations o f binding are observed. D ark-adapted sam ples, or those pre­ illuminated by an even number o f flashes, bind more inhibitor than sam ples preillum inated by an odd number o f flashes. Binding oscillations depend on inhibitor incubation tim e and on the seasonal adaptation o f the plants. The binding kinetics follow ing a single flash display three phases, the last two o f which can be correlated with reoxidation kinetics o f the secondary p h oto­ system II acceptor Qb, as determined by fluorescence measurem ents. Analysis o f the binding at DCM U concentrations up to 10"7 M free D C M U yields identical binding constants for dark-and flash preilluminated samples, but much less binding sites follow ing one flash. It is concluded that up to 10~7 M free DCM U, centers with bound Q b do not contribute significantly to total binding. Displacement o f Q b from the binding site is half-saturated at about 10-6 M D C M U , as m onitored via fluorescence induction. The data are considered strong support for the Velthuys 'inhibitor-Q i competition model'. 
  Reference    Z. Naturforsch. 39c, 397 (1984); received D ecem ber 1 1983 
  Published    1984 
  Keywords    Inhibitor Binding, Photosystem II, Binary O scillation, Chlorophyll Fluorescence 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0397.pdf 
 Identifier    ZNC-1984-39c-0397 
 Volume    39 
9Author    Salil Bose, R. M. Annar, M. Annan, C. J. ArntzenRequires cookie*
 Title    Increased Synthesis of Photosystem II in Triticum vulgare when Grown in the Presence of BAS 13-338  
 Abstract    Addition o f BAS 13-338 (4-chloro-5-dim ethylam ino-2-phenyl-3(2H)-pyridazinone) to a sus­ pension o f chloroplast thylakoids caused an increase in the / level o f chlorophyll fluorescence induction without affecting the F0 level and with a slight decrease in the Fmax level in a manner similar to the addition o f D C M U to a thylakoid suspension. A ddition o f BAS 13-338 also inhibited the rate o f Hill reaction H20 -» dichlorophenol indophenol with 50% inhibition occurring at about 10 hm BAS 13-338. The inhibition was not reversed by diphenyl carbazide used as an artificial electron donor to photosystem II. These results suggest that the site o f in h ib i­ tion by BAS 13-338 is between Q (next to the primary electron acceptor) and plastoquinone. When the plants were grown in the presence o f sublethal dose o f BAS 13-338, the follow ing changes were noted in the thylakoids o f the treated plants as com pared to the thylakoids isolated from the control plants: The F0 and the norm alized variable fluorescence (4F/F0) levels increased, chlorophyll a/b ratio decreased, chlorophyll/P 700 ratio increased. Furthermore, the rate o f photosystem II electron transport both under saturated intensity and the lim iting intensity of illumination increased, and the ratio o f plastoquinone to Q decreased. These observations have been interpreted as due to an increase in the ratio o f photosystem II to photosystem I in plants grown in the presence o f BAS 13-338. 
  Reference    Z. Naturforsch. 39c, 510 (1984); received D ecem ber 1 1983 
  Published    1984 
  Keywords    Photosynthesis, Electron Transport, Chlorophyll Fluorescence, Photosystem II, BAS 13-338 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0510.pdf 
 Identifier    ZNC-1984-39c-0510 
 Volume    39