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'Herbicides' in keywords Facet   Publication Year 1993  [X]
Facet   section ZfN Section C  [X]
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1993[X]
1Author    H. Adar Kless3, Michal Oren-Shamirb, ItzhakO. Hadc, M. Arvin Edelm, Wim VermaasaRequires cookie*
 Title    Protein Modifications in the D 2 Protein of Photosystem II Affect Properties of the Q B/Herbicide-Binding Environment  
 Abstract    The D 2 protein contains an extended loop (the D-de loop) between helices D and de at the reducing side o f photosystem II (PS II). Characterization o f D 2 mutants o f the cyanobacte­ rium Synechocystis sp. PCC 6803 has indicated that the length and amino acid com position o f the D-de loop are not critical for basic PS II functions, although most o f the residues in that region are conserved phylogenetically. Here we show using herbicide binding and electron-flow inhibition measurements that drastic modifications in the D-de loop o f the D 2 protein modify the interaction o f some PS II-directed herbicides with their binding niche. The stability o f (semi-)reduced Q B in its binding pocket is altered in at least two o f the mutants, as indicated by a shifted peak temperature o f the thermoluminescence signal originating from charge recombi­ nation involving QB. These results suggest a close functional association between the D-de loop o f the D 2 protein and the Q B/herbicide-binding environment, which is viewed as being coordinated mostly by re­ sidues o f the D 1 protein. This represents one o f the first examples o f m odification o f the Q B/ herbicide-binding domain by mutations in the D 2 protein. 
  Reference    Z. Naturforsch. 48c, 185—190 (1993); received November 23 1992 
  Published    1993 
  Keywords    Herbicides, Plastoquinone, Photosystem II, Thermoluminescence, Cyanobacteria 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0185.pdf 
 Identifier    ZNC-1993-48c-0185 
 Volume    48 
2Author    HartmutB. Stegmann, Paul Schuler, Stefan Westphal, Edgar WagnerRequires cookie*
 Title    Oxidative Stress of Crops Monitored by EPR  
 Abstract    Treatm ent of leaves of spinach, corn, and peas with the herbicides paraquat, am itrole or acifluorfen leads to oxidative stress resulting in a light driven drastically increased production of ascorbic acid radical (monodehydroascorbic acid, M DAA) which could be dem onstrated by in vivo EPR analysis. A discrimination of the M D A A form ation between the action of elec­ tron uncouplers and catalase inhibitors can be achieved by observation of the radical rise ki­ netics. Significant M DAA signal intensities are detected in the darkness likewise. These signals are probably due to the action of ascorbic acid oxidase activated by membrane destruction. 
  Reference    Z. Naturforsch. 48c, 766—772 (1993); received M arch 3/July 1 1993 
  Published    1993 
  Keywords    Herbicides, Paraquat, Amitrole, Ascorbic Acid Radicals 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0766.pdf 
 Identifier    ZNC-1993-48c-0766 
 Volume    48 
3Author    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 
4Author    KlausG. Tietjen, Wilfried Draber, John Goossens, JohannesR. Jansen, JoachimF. Kluth, Michael Schindler, Heinz-Jürgen, Wroblowsky Bayer, A. G.Requires cookie*
 Title    Binding of Triazines and Triazinones in the QB-Binding Niche of Photosystem II  
 Abstract    A series o f 20 triazines (derivatives o f 2-alkylam ino-4-benzylam ino-6-chloro-l,3,5-triazines) and 37 triazinones (derivatives o f 3-alkyl-4-am ino-6-phenyl-l,2,4-triazin-5-ones) is tested for inhibitory potency in photosynthetic electron flow through photosystem II o f wild type Chla-mydomonas reinhardtii and o f five mutants with aminoacid substitutions in the D 1 protein at valine 219, alanine 251, phenylalanine 255, serine 264, and leucine 275. The data are used for computer modelling o f .the possible location o f the com pounds within a three dimensional model o f the QB-binding niche o f the D 1 protein. 
  Reference    Z. Naturforsch. 48c, 205 (1993); received November 23 1992 
  Published    1993 
  Keywords    D 1 Protein, Herbicides, Molecular M odeling, Photosystem II, Q B-Binding Niche 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0205.pdf 
 Identifier    ZNC-1993-48c-0205 
 Volume    48