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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Archives of microbiology 121 (1979), S. 1-7 
    ISSN: 1432-072X
    Keywords: Rhizobium meliloti ; Symbiosis ; Influence of the RP4 plasmid on effectivity ; Cryptic plasmids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The occurrence of endogenous plasmid DNA in Rhizobium meliloti is reported. R. meliloti strains carrying RP 4 were used to work out a suitable plasmid isolation method. By sarcosyl lysis RP 4 plasmid DNA as well as cryptic plasmid DNA was isolated. Cryptic plasmid DNA possesses a buoyant density of 1.717 g cm-3 and shows a heterogeneity in contour length. Large plasmid molecules of 130 μm length were detected in the electron microscope. We also found that RP4 is able to restore the nitrogen fixation capacity of an ineffective R. meliloti strain.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Fresenius' Zeitschrift für analytische Chemie 287 (1977), S. 121-127 
    ISSN: 1618-2650
    Keywords: Best. von Calcium ; in Mineralien ; Isotopen-verdünnung/Massenspektrometrie ; Ionenaustauscher, Thermionen-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Ein Verfahren zur massenspektrometrischen Isotopenverdünnungsanalyse geringer Calciumkonzentrationen in Mineralien wurde entwickelt. Die einzelnen analytischen Teilschritte (Aufschlußverfahren mit Isotopenverdünnung, Calciumseparation und massenspektrometrische Messung) des Gesamtverfahrens werden beschrieben. Für einen 42Ca-Indicator wird die optimale Indicatorzugabe sowie Auswirkungen der massenspektrometrischen Messungen auf den Fehler des Analysenverfahrens diskutiert. Bei der chromatographischen Calciumabtrennung an einem stark sauren Ionenaustauscher wird eine vollständige Separation von Kalium erreicht. Der Calciumgehalt im Bereich von 0,15–0,004 Gew.-% zweier Kalifeldspäte und eines Lepidolithen wird mit externen relativen Standardabweichungen von 0,9–5,1% bestimmt.
    Notes: Summary A mass spectrometric isotope dilution analysis for the determination of small calcium contents is developed. The different steps (decomposition of the mineral including isotope dilution technique, calcium separation and mass spectrometric measurement) of the analytical procedure are described. For a 42Ca spike the optimum spike addition is calculated. The dependence of the analysis error on the mass spectrometric measurements is discussed. Using a chromatographic method with a strong acidic ion exchanger calcium can be completely separated from potassium. The calcium content in the range of 0.15–0.004% of two feldspars and of one lepidolite is determined with external relative standard deviations of 0.9–5.1%.
    Type of Medium: Electronic Resource
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