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  • 1
    ISSN: 1432-072X
    Keywords: ATP-citrate lyase ; Citric acid cycle ; Acetate oxidation ; ATP synthesis via substrate level phosphorylation ; Sulfate-reducing bacteria ; Desulfobacter postgatei
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Desulfobacter postgatei is an acetate-oxidizing, sulfate-reducing bacterium that metabolizes acetate via the citric acid cycle. The organism has been reported to contain a si-citrate synthase (EC 4.1.3.7) which is activated by AMP and inorganic phosphate. It is show now, that the enzyme mediating citrate formation is an ATP-citrate lyase (EC 4.1.3.8) rather than a citrate synthase. Cell extracts (160,000xg supernatant) catalyzed the conversion of oxaloacetate (apparent K m=0.2 mM), acetyl-CoA (app. K m=0.1 mM), ADP (app. K m=0.06 mM) and phosphate (app. K m=0.7 mM) to citrate, CoA and ATP with a specific activity of 0.3 μmol·min-1·mg-1 protein. Per mol citrate formed 1 mol of ATP was generated. Cleavage of citrate (app. K m=0.05 mM; V max=1.2 μmol · min-1 · mg-1 protein) was dependent on ATP (app. K m=0.4 mM) and CoA (app. K m=0.05 mM) and yielded oxaloacetate, acetyl-CoA, ADP, and phosphate as products in a stoichiometry of citrate:CoA:oxaloacetate:ADP=1:1:1:1. The use of an ATP-citrate lyase in the citric acid cycle enables D. postgatei to couple the oxidation of acetate to 2 CO2 with the net synthesis of ATP via substrate level phosphorylation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-072X
    Keywords: Desulfobacter hydrogenophilus ; Sulfate-reducing bacteria ; Autotrophy ; Citric acid cycle ; ATP-citrate lyase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The strict anaerobe Desulfobacter hydrogenophilus is able to grow autotrophically with CO2, H2, and sulfate as sole carbon and energy sources. The generation time at 30°C under autotrophic conditions in a pure mineral medium was 15 h, the growth yield was 8 g cell dry mass per mol sulfate reduced to H2S. Enzymes of the autotrophic CO2 assimilation pathway were investigated. Key enzymes of the Calvin cycle and of the acetyl CoA pathway could not be found. All enzymes of a reductive citric acid cycle were present at specific activities sufficient to account for the observed growth rate. Notably, an ATP-citrate lyase (1.3 μmol · min-1 · mg cell protein-1) was present both in autotrophically and in heterotrophically grown cells, which was rapidly inactivated in the absence of ATP. The data indicate that in D. hydrogenophilus a reductive citric acid cycle is operating in autotrophic CO2 fixation. Since other autotrophic sulfate reducers possess an acetyl CoA pathway for CO2 fixation, two different autotrophic pathways occur in the same physiological group.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    X-Ray Spectrometry 3 (1974), S. 176-178 
    ISSN: 0049-8246
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Description / Table of Contents: The determination of film thicknesses by XRFA is known from the literature. In most cases these methods are based on a comparison with defined reference films. Together with theoretical considerations a new method is developed, where no reference films are needed. An estimation on the accuracy of this method and measurements used in an energy dispersive system are discussed, and the method is evaluated.
    Notes: Die röntgnfluoreszenzanalytiche Bestimmung der Massenbelegung dünner Schichten ist literaturbekannt. Diese Methoden bauen zumeist auf einem Vergleich mit Proben difinierter. Massenbelegung auf. Es wird von der Theorie her gezeit, wie eine eichprobenfreie Messung möglich ist. Neben einer Abschätzung der mit dieser Methode verbundenen Fehler Werden die Messungen mit einem energiedispersiven Spektrometer und die rechnerische Auswertung behandelt.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 355 (1967), S. 145-151 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Aluminium chloride gives on reduction in pyridine a radical solution whose ESR spectrum indicates spin coupling with two Al, two N and two H nuclei, the latter being protons in 6-position. It is derived that bis-(N-dichloroaluminium)-1,1′,2,2′-tetrahydro-4,4′-bipyridyl is formed, which dissociates into radicals at the C—C linkage between the two dihydropyridyl groups. This suggestion is also based on the formation of the same radical from Cl2AlH and 4,4′-bipyridyl, and on its observed NMR contact shifts.
    Notes: Aluminiumchlorid bildet bei der Reduktion in Pyridin eine (Abb. 1a, b) radikalische Lösung, deren ESR-Spektrum durch die Kopplung des Elektronenspins mit zwei Al-, zwei N- und zwei H-Kernen zu deuten ist. Versuche mit partiell deuterierten Pyridinen zeigen, daß es sich bei den Wasserstoffatomkernen um Protonen in 6-Stellung handeln muß. Die aus diesen Ergebnissen abgeleitete Struktur ist die eines Bis-(N-dichloraluminium)-1,1′,2,2′-tetrahydro-4,4′-bipyridyls, das an der Verknüpfungsstelle zweier Dihydropyridylreste in Radikale zu dissoziieren vermag. Gestützt wird diese Formulierung durch die Addition von Dichloralan Cl2AlH, an 4,4′-Bipyridyl, bei der das gleiche Radikal entsteht. Zur Ergänzung der ESR-Kopplungskonstanten wurden die „paramagnetischen Kontaktverschiebungen“ im NMR-Spektrum gemessen.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 14 (1901), S. 207-208 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 17 (1904), S. 1505-1509 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 18 (1905), S. 254-255 
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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