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'Absorbance Difference Spectra' in keywords Facet   section ZfN Section C  [X]
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1990 (1)
1988 (1)
1Author    Martine Bertrand, Barbara Bereza, Esther DujardinRequires cookie*
 Title    Evidence for Photoreduction of NADP + in a Suspension of Lysed Plastids from Etiolated Bean Leaves  
 Abstract    It has been investigated if photoreduction of NADP + (detected by absorption spectroscopy) may take place in lysed plastids within minutes of exposure to light. This process was made possible by removal of oxidants from the reaction mixture. Lysed plastids were suspended in a medium containing NADP + , catalase, glucose oxidase and glucose; exposure to light simultane-ously to addition of ferredoxin and ferredoxin-NADP + reductase, resulted in increased absorb-ance in the band around 340 nm, while addition of 3-phosphoglycerate resulted in the disappear-ance of this band. Ferredoxin and ferredoxin-NADP + reductase are only effective when photo-activation takes place before their addition to the medium. 
  Reference    Z. Naturforsch. 43c, 443—448 (1988); received January 25 1988 
  Published    1988 
  Keywords    NADPH, NADP + Photoreduction, Etioplasts, Absorbance Difference Spectra, Phaseolus vulgaris 
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 TEI-XML for    default:Reihe_C/43/ZNC-1988-43c-0443.pdf 
 Identifier    ZNC-1988-43c-0443 
 Volume    43 
2Author    JeffA. Nemson, Anastasios MelisRequires cookie*
 Title    Light-Induced Oxidation-Reduction Reactions of Photosystem II in Dichlorophenyl-dimethyl Urea (DCM U) Inhibited Thylakoids  
 Abstract    Illumination o f thylakoid membranes in the presence o f 3-(3',4'-dichlorophenyl)-1,1-di-methyl urea (D C M U) causes the reduction o f the primary quinone acceptor QA o f photosys­ tem II (PS II) and the storage o f a positive charge on the donor side o f the photochem ical reac­ tion center. These oxidation-reduction reactions are accompanied by characteristic changes o f absorbance in the ultra-violet region o f the spectrum. The PS II-related absorbance difference spectra (2 5 0 -3 5 0 nm) were compared in control and hydroxylamine-treated thylakoid mem­ branes, and in thylakoids suspended in the presence o f carbonyl cyanide-/7-(trifluoromethoxy)-phenylhydrazone (FCCP). The light minus dark difference spectra were dominated by the QA minus QA difference spectrum. Qualitatively, the three spectra were identical in the 3 0 0 -3 5 0 nm region, however, they showed distinct differences in the 2 5 0 -3 0 0 nm region. The latter arose because o f different contributions from the donor side o f PS II in the thylakoid membrane o f the three samples. The result suggested that FCCP acts as the ultimate electron donor in D C M U -poisoned chloroplasts. Therefore, the absorbance difference spectrum in the presence o f FCCP reflected a contribution from the QA minus QA com ponent only. D econvolu­ tion o f the absorbance difference spectra o f control and hydroxylamine-treated thylakoids yielded difference spectra attributed to the oxidation o f a com ponent on the donor side o f PS II. This com ponent did not conform with the known M n(III) — ■ > M n(IV) transition. R ath­ er, it indicated the oxidation o f a modified form o f Mn in the presence o f D C M U , probably a Mn(II) —> M n(III) transition. The results are discussed in terms o f the use o f D C M U -poisoned thylakoid membranes in the quantitation o f the primary quinone acceptor Q A by spectro-photom etric approaches. 
  Reference    Z. Naturforsch. 45c, 258 (1990); received July 25/August 21. 1989 
  Published    1990 
  Keywords    Absorbance Difference Spectra, Photosystem II, Electron Transport, Primary Quinone Acceptor, Electron D onor Tyrosine 
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 TEI-XML for    default:Reihe_C/45/ZNC-1990-45c-0258.pdf 
 Identifier    ZNC-1990-45c-0258 
 Volume    45