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'Cyanobacterium' in keywords Facet   Publication Year 1997  [X]
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1Author    Refat Abdel-Basset, KlausP. BaderRequires cookie*
 Title    Characterization of Hydrogen Photoevolution in Oscillatoria chalybea Detected by Means of Mass Spectrometry  
 Abstract    The filamentous non-heterocystous cyanobacterium Oscillatoria chalybea is capable to photoevolve molecular hydrogen when the cells are flushed to anaerobiosis with nitrogen or argon and exposed to short light flashes or continuous light. The light-induced hydrogen gas exchange of Oscillatoria chalybea has been investigated by direct determ ination of dynamic changes in the hydrogen partial pressure at m/e=2 in the H/D collector of a mass spectromet-ric set-up. By means of this technique also the time curves of the light-induced hydrogen gas exchange could be directly recorded. Depending on the chlorophyll concentration in the measuring cell we observed an increasing hydrogen content of the aqueous Oscillatoria sus­ pension i.e. a dark evolution of molecular hydrogen. Upon the onset of light an initial rise of the H 2-signal was observed which was increasingly mixed or followed by a hydrogen uptake. The capability to photoevolve molecular hydrogen was maximal with young cultures and decreased with increasing age. The hydrogen evolution signals require relatively short dark adaptation to get pronounced; few seconds suffice for 2/3 of the hydrogen evolution amplitude. Prolonged dark adaptation maximizes the flash amplitudes. The hydrogen evolu­ tion signals do not deactivate by low flash frequency Oscillatoria chalybea evolves molecular hydrogen following growth on nitrogen free or nitrate containing medium. Increase of the oxygen partial pressure of the assays completely abolishes the hydrogen evolution signals with an I50-value of 6 ^im. 
  Reference    Z. Naturforsch. 52c, 775—781 (1997); received September 8/October 17 1997 
  Published    1997 
  Keywords    Photosynthesis, Mass Spectrometry, Hydrogen Photoevolution, Cyanobacterium 
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 TEI-XML for    default:Reihe_C/52/ZNC-1997-52c-0775.pdf 
 Identifier    ZNC-1997-52c-0775 
 Volume    52 
2Author    Gottfried Martin, Peter BögerRequires cookie*
 Title    Two Ways of Hydrogen Peroxide Formation in the Oxidative Inactivation of Cyanobacterial Glutamine Synthetase  
 Abstract    Using crude extracts from the cyanobacterium Anabaena variabilis glutamine synthetase (GS) activity was rapidly irreversibly reduced to about 60% during dark incubation ("sponta­ neous GS inactivation"). An additional decrease was observed by the addition of ammonia in the light ("ammonia-m ediated inactivation"). Both effects were prevented by EDTA, MnCl2 or catalase indicative of the involvement of H 20 2. This is a key interm ediate in oxida­ tive enzyme inactivation. In both spontaneous and am monia-mediated GS inactivation H 20 2 is produced in different ways. Spontaneous inactivation is prevented by depletion of reduced pyridine nucleotides which apparently donate electrons to produce H 20 2. Fractionation of the crude extract showed that the light-enhanced GS inactivation by ammonia required the presence of thylakoid membranes. The photosynthesis inhibitor DCM U decreased GS inacti­ vation by ammonia. For the inactivation in the light apparently H 20 2 is produced from super­ oxide during photosynthetic electron transport. 
  Reference    Z. Naturforsch. 52c, 812—816 (1997); received August 12 1997 
  Published    1997 
  Keywords    Glutamine Synthetase, Protein Oxidation Ammonia Effect, Photosynthetic Hydrogen Peroxide Production, Cyanobacterium, Anabaena variabilis 
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 TEI-XML for    default:Reihe_C/52/ZNC-1997-52c-0812.pdf 
 Identifier    ZNC-1997-52c-0812 
 Volume    52