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'Membrane Potential' in keywords Facet   Publication Year 1991  [X]
Facet   section ZfN Section C:Volume 046  [X]
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1Author    C. Hristof Klugham, Er, Ulrich SchreiberRequires cookie*
 Title    Analysis of Light-Induced Absorbance Changes in the Near-Infrared Spectral Region I. Characterization of Various Components in Isolated Chloroplasts  
 Abstract    Light-induced absorbance changes in the near-infrared (N IR) spectral region (7 0 0 -9 5 0 nm) are analyzed in isolated spinach chloroplasts using pulsed light-emitting diodes as modulated measuring light sources. With chloroplasts under coupled conditions the light-induced signal is dominated by a relatively slow scattering change displaying a flat difference spectrum. More specific changes can be distinguished by faster induction and relaxation kinetics and in the presence o f valinomycin/nigericin which prevents scattering changes. Besides the dominant P700 change, with a narrow bleaching band around 703 nm and a broad absorbance increase between 750 and 850 nm (peak at 815 nm) the following absorbance changes were identified in the NIR: 1) An absorbance increase caused by plastocyanin (PC) oxidation, with a relatively flat spectrum. 2) An absorbance decrease gaining amplitude towards longer wavelengths, which reflects reduction o f a low potential acceptor o f PS I different from ferredoxin. 3) A field indicating absorbance decrease peaking around 730 nm, the properties o f which correspond to those o f P 515. 4) An uncoupler insensitive absorbance decrease stimulated by dark adaptation and anaero­ bic conditions, the difference spectrum o f which resembles that o f ferredoxin reduction. The relative contributions o f P700 and PC to the overall oxidized-reduced difference spec­ trum are determined by redox titration. At 706 nm, 815 nm and 950 nm the P 700/PC is -119/ 19, 67/37 and 31/69, respectively. From these ratios and the molar extinction coefficients a molar P 700/PC stoichiometry o f 1 /3 is determined. 
  Reference    Z. Naturforsch. 46c, 233 (1991); received November 19 1990/January 2 1991 
  Published    1991 
  Keywords    Plastocyanin, Membrane Potential, Ferredoxin, Light Scattering, Photosynthesis 
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 TEI-XML for    default:Reihe_C/46/ZNC-1991-46c-0233.pdf 
 Identifier    ZNC-1991-46c-0233 
 Volume    46