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1987 (1)
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1981 (1)
1Author    Henrik Laasch, Klaus Pfister, Wolfgang UrbachRequires cookie*
 Title    Comparative Binding of Photosystem II — Herbicides to Isolated Thylakoid Membranes and Intact Green Algae  
 Abstract    The binding of the photosystem II herbicides diuron (DCM U), atrazine (s-triazine), ioxynil and dinoseb (substituted phenols) to isolated spinach thylakoids was saturated in less than 2 min in the dark. In intact cells of the green alga Ankistrodesmus b. it took 10 to 20 min to reach the binding equilibrium. Binding affinity of diuron, atrazine, dinoseb, measured as equilibrium binding constants, was found to be comparable in isolated thylakoids and intact algal cells. For ioxynil, reduced binding affinity was observed in algae. The concentration of binding sites in thylakoids and intact cells was determined to be 300-500 chl/inhibitor binding site, suggesting a 1:1 stoichiometry between bound herbicide and electron transport chains. In intact cells only the phenol herbicides ioxynil and dinoseb showed increased concentrations of binding sites. Strong correlation of herbicide binding and inhibition o f electron transport was found for diuron in isolated thylakoids and intact cells. In thylakoids this is valid also for atrazine and dinoseb. For ioxynil a difference between the amount of binding and inhibition was found. This correlation o f herbicide binding and inhibition proves that binding specifically occurs at the inhibition site at photosystem H. In addition to the specific binding, for all four herbicides studied, (except for ioxynil in thylakoids) unspecific binding was observed in thylakoids as well as in algae, which was not related to inhibition. 
  Reference    Z. Naturforsch. 36c, 1041—1049 (1981); received July 13 1981 
  Published    1981 
  Keywords    Herbicides, Herbicide Binding, Photosynthesis, Thylakoids, Algae 
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 TEI-XML for    default:Reihe_C/36/ZNC-1981-36c-1041.pdf 
 Identifier    ZNC-1981-36c-1041 
 Volume    36 
2Author    Z. NaturforschRequires cookie*
 Title    Increased Binding of | 14C|Ioxynil in Unicellular Green Algae under Anaerobiosis and by Addition of Other Phenolic Herbicides or Uncouplers  
 Abstract    Binding o f the phenol-type herbicide ioxynil in intact algal cells is strongly increased under anaerobic conditions. This increase is most pronounced at low concentrations o f bound ioxynil (< 3 nm ol/m g chlorophyll). The affinity o f binding sites is im proved, rather than new sites are created. Other phenol-type herbicides, as well as uncouplers like carbonylcyanidechlorophenylhydra-zone, also significantly increase ioxynil binding in algae. Binding o f D C M U -typ e herbicides, however, was not affected. These results demonstrate high variability o f ioxynil binding in algal cells and are discussed in respect o f low affinity binding. 
  Reference    Z. Naturforsch. 39c, 402 (1984); received D ecem ber 1 1983 
  Published    1984 
  Keywords    Herbicide Binding, Ioxynil Uncoupler, Anaerobiosis, A lgae 
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 TEI-XML for    default:Reihe_C/39/ZNC-1984-39c-0402.pdf 
 Identifier    ZNC-1984-39c-0402 
 Volume    39 
3Author    WimF J Vermaas, JohnG K Williams, CharlesJ. ArntzenRequires cookie*
 Title    Site-Directed Mutations of Two Histidine Residues in the D 2 Protein Inactivate and Destabilize Photosystem II in the Cyanobacterium Synechocystis 6803  
 Abstract    Site-directed m utations were created in the cyanobacterium Synechocystis 6803 to alter specific histidine residues o f the photosystem II (PS II) D 2 protein. In one mutant (tyr-197). the his-197 residue was replaced by tyrosine, in another mutant (asn-214), his-214 was changed into asparagine. The tyr-197 mutant did not show any low-tem perature fluorescence attributable to PS II. but contained a PS II chlorophyll-protein, CP-47, in significant quantities. A nother PS II chlorophyll-protein, CP-43, was absent, as was PS II-related herbicide binding. The asn-214 mutant showed a blue-shifted low-temperature fluorescence maximum around 682 nm. but did not have a significant amount of membrane-incorporated CP-43 or CP-47. Herbicide binding was also absent in this mutant. These data indicate a very important role o f the his-197 and his-214 residues in the D 2 protein, and are interpreted to support the hypothesis that the D 2 protein and the M subunit from the photosynthetic reaction center of purple bacteria have analogous func­ tions. According to this hypothesis, his-197 is involved in binding of P680. and his-214 forms ligands with Q A and Fe:+. In absence o f a functional D 2 protein, the PS II core com plex appears to be destabilized as evidenced by loss o f chlorophyll-proteins in the mutants. 
  Reference    Z. Naturforsch. 42c, 762—768 (1987); received D ecem ber 30 1986 
  Published    1987 
  Keywords    Site-D irected M utagenesis, Herbicide Binding, Photosystem II Proteins, Photosynthesis, Cyanobacteria 
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 TEI-XML for    default:Reihe_C/42/ZNC-1987-42c-0762.pdf 
 Identifier    ZNC-1987-42c-0762 
 Volume    42