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1991 (1)
1975 (2)
1Author    SeymourSteven BrodyRequires cookie*
 Title    Surface Properties of Monomolecular Films of Reduced Plastocyanin at a Nitrogen-Water Interface  
 Abstract    The area/molecule (A) and surface potential {A V) of reduced plastocyanin (pcyan) was measured as a function of pH. At pH 7.5 a maximum is observed for A while a minimum is ob­ served for A V . At a surface pressure of 5 dyn/cm the maximum ^ 5 = 378 Ä 2 and minimum A V 5 = 335 mV. There is an interaction between pcyan and chlorophyll (Chi) in mixed films. As shown by a decrease of A and V compared to theoretically calculated volues. The largest decrease occurs at a mol ratio of about 2 pcyan: 1 Chi. When mixed films are irradiated in air no changes in surface properties are observed. Irradiation of mixed films of reduced pcyan and Chi in nitrogen results in a decrease in A and an increase of AV. The maximum decrease occurs at a mol ratio of pcyan/Chl between 1.5 and 2.0. The direction of change of A is consistant with a conversion of reduced pcyan to oxidized pcyan. 
  Reference    (Z. Naturforsch. 30c, 318 [1975]; received October 4 1974) 
  Published    1975 
  Keywords    Plastocyanin, Photosynthesis, Monolayers, Model Membranes 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0318.pdf 
 Identifier    ZNC-1975-30c-0318 
 Volume    30 
2Author    GeorgH. Schmid, Alfons Radunz, Wilhelm MenkeRequires cookie*
 Title    The Effect of an Antiserum to Plastocyanin on Various Chloroplast Preparations  
 Abstract    A monospecific antiserum to tobacco plastocyanin agglutinates strom a-free sw ellable chloroplasts from wild type tobacco, (N ico tia n a tabacum var. John William's Broadleaf) from the tobacco aurea mutant Su/su2, (N ico tia n a tabacum var. Su/su2) from A ntirrh in um m aju s and spinach (Spi-nacia o lera cea). In this condition the antiserum inhibits linear photosynthetic electron flow in tobacco and spinach chloroplasts. This inhibition of electron transport as well as the agglutination are not observed if the chloroplasts have been sonicated prior to antiserum addition. This is due to the fact that plastocyanin is removed by ultrasonication. The antiserum stimulates a number of photophosphorylation reactions in tobacco chloroplasts. This stimulation is always larger in the aurea mutant chloroplasts and in chloroplasts from yellow leaf patches of a variegated tobacco mutant (N . tabacu m , var. N C 95) than in the green type chloroplasts. The stimulation appears to be a consequence of the inhibition of linear electron transport. The antiserum does not affect PMS-mediated cyclic photophosphorylation in tobacco chloroplasts from the wild type whereas the reaction appears stimulated in the tobacco mutant chloroplasts. However, menadione-mediated cyclic photo­ phosphorylation is inhibited upon addition of the antiserum. The same is true for noncyclic photo­ phosphorylation coupled to electron transport in the aerobic system diaminodurene/ascorbate — > methylviologen in the presence of N-tetraphenyl-p-phenylenediamine in spinach chloroplasts. If the lamellar system of A n tirrh in u m and spinach has lost its swellability neither agglutination nor inhibition of electron transport is observed. However, also in this state antibodies to plasto­ cyanin are specifically adsorbed onto the surface of the thylakoid membrane. This state which is characterized by a morphologically well preserved lamellar system is realized in chloroplast prepa­ rations from A n tirrh in um and spinach and is termed stroma-freed, chloroplasts. In both states of the molecular structure of the thylakoid membrane, plastocyanin is located in the outer surface of the thylakoid. However, it cannot be excluded that functioning plastocyanin is also located in the interior of the thylakoid membrane. 
  Reference    (Z. Naturforsch. 30c, 201 [1975]; received December 9 1974) 
  Published    1975 
  Keywords    Photosynthesis, Plastocyanin, Antibodies, Chlorophyll-deficient Tobacco Mutants 
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 TEI-XML for    default:Reihe_C/30/ZNC-1975-30c-0201.pdf 
 Identifier    ZNC-1975-30c-0201 
 Volume    30 
3Author    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