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'Histidine' in keywords
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1993 (2)
1977 (1)
1Author    U. Hegde, S. Padhye, L. Kovács, A. Vozár, S. DemeterRequires cookie*
 Title    Modification of Histidine Residues of Photosystem II by Diethyl Pyrocarbonate Inhibits the Electron Transfer between the Primary (QA) and Secondary (QB) Quinone Acceptors  
 Abstract    The effect o f diethyl pyrocarbonate (D EPC) on the photosynthetic electron transport was investigated in isolated spinach thylakoids by partial electron transport rate and thermolumi­ nescence measurements. Incubation o f thylakoids at pH 6.5 with 5 mM DEPC for 15 min re­ sulted in a considerable inhibition o f electron transport from water to dichlorophenolindo-phenol. The inhibition was only partially releaved by addition o f the donor, diphenylcarbazide indicating the effect o f DEPC both on the donor and acceptor sides o f PS II. In the thermolu­ minescence glow curve DEPC-treatm ent abolished the B band (S2Q B~ radiative charge recom ­ bination) at 30 °C with a concom itant appearance o f the Q band (S2QA~ charge recombina­ tion) at 10 °C. This suggests that in isolated thylakoids possessing an active water-splitting sys­ tem DEPC affects the electron transfer from QA to QB but does not inhibit the electron transport from manganese to QA during the S t—>S2 transition o f the water-splitting system. At the acceptor side o f PS II the targets o f DEPC are probably the histidines which are coordinat­ ed to the non-hem e iron. Illumination o f thylakoids at -8 0 °C following DEPC addition after two preflashes at 5 °C resulted in the replacement o f the A (A T) thermoluminescence band at -3 0 °C with a band appearing at -1 5 °C. This observation can be explained by the effect o f DEPC on a donor side histidine com ponent participating in the generation o f the A (A T) band. Consequently, in the interpretation o f results obtained by DEPC treatment o f PS II, both the donor and acceptor side effects o f DEPC should be considered. 
  Reference    Z. Naturforsch. 48c, 896—9 (1993); received May 4/September 6 1993 
  Published    1993 
  Keywords    Diethyl Pyrocarbonate, Histidine, Photosynthesis, Photosystem II, Thermoluminescence 
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 TEI-XML for    default:Reihe_C/48/ZNC-1993-48c-0896.pdf 
 Identifier    ZNC-1993-48c-0896 
 Volume    48 
2Author    G. Erhard, N. Schrauzer, PaulA. Doemeny, JohnG. PalmerRequires cookie*
 Title    The Chemical Evolution o f a Nitrogenase Model, XXII. Reduction of Acetylene with Catalysts Derived from Molybdate, Homocitric Acid and N-M ethylimidazole and a Proposal Concerning the Active Site of Functional Azotobacter Nitrogenases  
 Abstract    Based on model experiments it is suggested that the reduction o f substrates by nitrogenase occurs at a m ononuclear site containing molybdenum, homocitrate and the imidazole com ponent of his-442 o f the apoenzyme, generated from the FeMo-co by a reversible dissociation of the Fe7S8 unit from the M oFe7S8 cluster in a redox-linked process. 
  Reference    Z. Naturforsch. 48b, 1295—1298 (1993); received May 14 1993 
  Published    1993 
  Keywords    Nitrogenase, Acetylene Reduction, M olybdenum-Catalyzed, Homocitric Acid, Histidine, Imidazole 
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 TEI-XML for    default:Reihe_B/48/ZNB-1993-48b-1295_n.pdf 
 Identifier    ZNB-1993-48b-1295_n 
 Volume    48 
3Author    J. Iř, Ina Kopoldová, ŠtĕpánH. RnčiřRequires cookie*
 Title    Gamma-Radiolysis of Aqueous Solution of Histidine  
 Abstract    The dependence of Gi(— M) values of histidine on the concentration of irradiated 10-4 —10-1 m solutions, pH and the presence of 0 2 , N20 and sec-butyl alcohol was investigated. In oxygen-free medium the maximum radiation sensitivity of histidine was found at pH 5 — 8 ; in oxygenated solutions it was shifted to the 6 — 11 pH range. The formation of radiation products was also studied. The course of radiation decomposition of histidine depends on the presence of oxygen and on the pH of irradiated solution. 
  Reference    (Z. Naturforsch. 32c, 482 [1977]; received January 28/April 19 1977) 
  Published    1977 
  Keywords    Gamma-Radiolysis, Histidine, Aqueous Solution, pH and Concentration Dependence, Radiation Products 
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 TEI-XML for    default:Reihe_C/32/ZNC-1977-32c-0482.pdf 
 Identifier    ZNC-1977-32c-0482 
 Volume    32