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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 68 (1969), S. 227-235 
    ISSN: 1432-072X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Dihydrouracil, 3-Ureidopropionat und β-Alanin, die Intermediärprodukte des reduktiven Cytosinabbaues, wurden durch Zellen von Hydrogenomonas facilis als Kohlenstoff- und Stickstoffquelle verwertet, Barbitursäure und Malonsäure, die Intermediärprodukte des oxidativen Abbaues, dagegen nicht. Während der Inkubation mit Extrakten aus Zellen, die mit Cytosin als N-Quelle gewachsen waren, wurde Uracil zu Dihydrouracil, 3-Ureidopropionat und β-Alanin umgesetzt. Barbitursäure und Harnstoff waren hierbei nicht nachweisbar. Nach Anzucht mit Cytosin waren die Enzyme Cytosin-Desaminase, Dihydrouracil-Dehydrogenase, Dihydrouracil-Hydrase und 3-Ureidopropionase, nicht aber Uracil-Oxidase in zellfreien Extrakten nachweisbar. Gegenüber den mit NH4Cl gewachsenen Zellen zeigten die mit Cytosin herangezogenen Zellen eine deutlich erhöhte spezifische Aktivität an Dihydrouracil-Dehydrogenase und Dihydrouracil-Hydrase, nicht aber an Cytosin-Desaminase. Diesen Befunden zufolge unterliegen die Pyrimidinderivate Cytosin und Uracil in Hydrogenomonas facilis einem reduktive Abbau.
    Notizen: Summary Dihydrouracil, 3-ureidopropionate and β-alanine, intermediates involved in the reductive degradation of cytosine, were utilized as a carbon and nitrogen source by cells of Hydrogenomonas facilis. Barbiturate and malonate, intermediates of the oxidative pathway, were not utilized. Uracil was converted to dihydrouracil, 3-ureidopropionate and β-alanine during incubation with extracts from cells grown with cytosine as a nitrogen source. Barbiturate and urea were not detected under these conditions. The enzymes cytosine deaminase, dihydrouracil dehydrogenase, dihydrouracil hydrase and 3-ureidopropionase but not uracil oxidase were demonstrated in cell-free extracts from cells grown with cytosine. The specific activity of dihydrouracil dehydrogenase and dihydrouracil hydrase but not of cytosine deaminase was significantly higher in extracts from cytosine grown cells, as compared with extracts from cells grown with ammonia. These data indicate that cytosine and uracil undergo a reductive degradation in cells of Hydrogenomonas facilis.
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 81 (1972), S. 178-196 
    ISSN: 1432-072X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary During nitrogen starvation, a 20- to 250-fold increase in specific urease activity was observed in extracts of P. aeruginosa, P. fluorescens, Hydrogenomonas, M. denitrificans, M. cerificans and B. megaterium. In contrast to these species, high levels of urease were observed in P. vulgaris strains and in S. ureae under all growth conditions. No urease was detectable in strains of E. coli, S. marcescens and B. polymyxa, regardless of growth conditions. Incubated in the absence of an exogenous nitrogen source, the specific urease activity increased during a period of 10 to 20 h in P. aeruginosa, Hydrogenomonas and M. denitrificans. Phosphate starvation did not significantly effect urease formation in these strains. The increase in specific urease activity was found to be repressed by exogenous nitrogen sources, including urea. Inhibition by chloramphenicol, other inhibitors, and by the lack of oxygen or fructose, indicated that a derepressive urease formation may occur in these strains. The involvement of traces of urea possibly released from endogenous sources during starvation is discussed.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 69 (1969), S. 138-148 
    ISSN: 1432-072X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Nach Behandlung mit 1-Nitroso-3-nitro-1-methylguanidin und nach Anreicherung in einem penicillinhaltigen Medium wurden von Hydrogenomonas facilis 35 Mutanten isoliert, die Uracil nicht mehr als N-Quelle zu nutzen vermochten. Eine Gruppe dieser Mutanten bildete keine Dihydrouracil-Dehydrogenase und verwertete Thymin, Orotsäure und Uracil nicht mehr. Eine zweite Gruppe hatte die Fähigkeit verloren, Dihydrouracil-Hydrase zu bilden und konnte Uracil, Orotsäure, Thymin, Dihydrouracil und Dihydrothymin nicht mehr verwerten. Während des Wachstums mit Cytosin wurde durch die erste Gruppe dieser Mutanten Uracil und durch die zweite Gruppe Dihydrouracil in das Nährmedium ausgeschieden. Die Enzyme Dihydrouracil-Dehydrogenase und Dihydrouracil-Hydrase waren in Zellen, die mit Cytosin, Uracil, Thymin oder Orotsäure angezogen worden waren, mit wesentlich höherer spezifischer Aktivität nachweisbar als in Zellen, die mit Ammoniumchlorid gewachsen waren. Dihydroorotsäure-Dehydrogenase und Dihydroorotsäure-Hydrase waren in den zellfreien Extrakten in keinem Fall nachweisbar. Die Befunde weisen daraufhin, daß Uracil und Thymin bei H. facilis durch eine unspezifische Dehydrogenase und Dihydrouracil und Dihydrothymin durch eine unspezifische Hydrase umgesetzt werden, und daß diese Enzyme in Gegenwart von Uracil, Thymin oder Orotsäure induktiv gebildet werden.
    Notizen: Summary 35 mutant strains, unable to utilize uracil as a nitrogen source, were isolated from Hydrogenomonas facilis following treatment with 1-nitroso-3-nitro-1-methylguanidine and enrichment in a penicillin containing medium. One group of these mutants lacked dihydrouracil dehydrogenase and did not utilize thymine, orotic acid and uracil. A second group of mutants had lost the ability to form dehydrouracil hydrase and was unable to utilize uracil, orotic acid, thymine, dihydrouracil and dihydrothymine. The first group of these mutants excreted uracil, the second group dihydrouracil into the medium during growth with cytosine. The enzymes dihydrouracil dehydrogenase and dihydrouracil hydrase were present in much higher specific enzyme activities in cells grown with cytosine, uracil, thymine or orotic acid than in ammonia grown cells. Dihydroorotic dehydrogenase and dihydroorotase could not be demonstrated in cell-free extracts. These data indicate that both uracil and thymine are utilized as substrates by a non-specific hydrogenase and that both dihydrouracil and dihydrothymine are utilized by a non-specific hydrase. Both these enzymes are induced in presence of uracil, thymine or orotic acid in cells of Hydrogenomonas facilis.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    Archives of microbiology 60 (1968), S. 172-181 
    ISSN: 1432-072X
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Hydrogenomonas facilis verwertet Thymin, Cytosin und Uracil als N-Quelle, Hydrogenomonas H 16 dagegen nur Cytosin. Durch Hydrogenomonas facilis wird Cytosin vollständig abgebaut, durch Hydrogenomonas H 16 lediglich desaminiert, wobei das entstehende Uracil in der Nährlösung angehäuft wird. In zellfreien Extrakten aus Hydrogenomonas H 16, die mit Cytosin als einziger N-Quelle gewachsen waren, wurde Cytosindesaminase-Aktivität im gekoppelten enzymatischen Test nachgewiesen, wobei Glutaminsäuredehydrogenase als Hilfsenzym diente. Mit Ammoniumchlorid herangezogene Zellen zeigten während der Indubation in Cytosin-haltigem Medium einen 18fachen Anstieg der spezifischen Cytosindesaminase-Aktivität.
    Notizen: Summary Hydrogenomonas facilis utilizes thymine, cytosine, and uracil as nitrogen sources; Hydrogenomonas H 16, however, only cytosine. Cytosine is completely metabolised by Hydrogenomonas facilis, but is only deaminated by Hydrogenomonas H 16 and the resulting uracil accumulates in the culture medium. Cytosine deaminase activity was demonstrated in cell-free preparations from Hydrogenomonas H 16 which had been grown with cytosine as the sole nitrogen source. Enzyme activity was measured using a coupled enzyme assay in which glutamic acid dehydrogenase served as an accesory enzyme. An 18-fold increase in cytosine deaminase activity was observed in ammonia-grown cells during the incubation in a cytosine containing medium.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 11 (1981), S. 0 
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology letters 23 (1984), S. 0 
    ISSN: 1574-6968
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Biologie
    Notizen: Abstract Streptococcus faecium strain 25 produced a bacteriocin (enterococcin Sf25), metabolized sucrose and contained three plasmids of 2.4, 4.7 and 13.0 MDa. Plasmids Sfp2.4 and Sfp4.7 were cotransferred in a filter mating procedure to sucrose negative and bacteriocin negative S. faecium strain M16. Strain M16 harboured a nonselftransferable plasmid Sfp 19.1 MDa, which was responsible for erythromycin resistance. Transcipient cells of S. faecium M16 contained the 19.1-MDa plasmid and plasmids Sfp2.4 and Sfp4.7, produced the enterococcin Sf25 and gained the ability to degrade sucrose.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 6204-6208 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Changes in the impedance, ≈600%/Oe, at axial fields less than 1 Oe have been observed in the presence of a 90 kHz, few mA current through a soft, nearly zero magnetostrictive wire. In this 125 μm diameter CoFeSiB amorphous wire we observe a total change of 160% at the maxima of the impedance in dc fields less than 2 Oe. A systematic study of the role of induced anisotropy in the axial, circumferential, and helical directions on the magneto-impedance shows that the largest effect is seen in the wire annealed to obtain circumferential easy axis using a 15 mA ac current passing through it. Both the axial hysteresis loops and the observed I-V characteristics reflect the induced anisotropies. The observed dependence of the inductance change on the type of the anisotropy induced in these wires can be modeled in terms of an interplay between the induced anisotropy, reversing ac field, and the axial dc field.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2039-2041 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The development of a versatile tool to quantify magnetic anisotropies in continuous and patterned magnetic thin films is reported. The technique involves measuring the magnetooptic response to a rotating magnetic field. Similarly to mechanical torque techniques, a single measurement obtains both the anisotropy constants and their symmetry axes distribution. The technique has been applied to analyze arrays of submicrometer stripe-shaped Fe (001) elements with different interelement separations (s). For s larger than 1 μm, the anisotropy associated with the stripes is independent on separation, with a value of the effective uniaxial anisotropy constant very consistent with theoretical estimations for these systems. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3091-3093 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The magnetic properties of 200 Å epitaxial Fe (001)/MgO (001) tiling are studied as a function of tile size and separation. For edge sizes above ∼3 μm, the individual tiles maintain the single domain behavior while below ∼3 μm the tiles break into domains due to demagnetizing effects. In addition, below an inter tile separation threshold of about 0.9 μm, a single tile magnetization switch provokes a reversal cascade in all the tiles; while, above this threshold, the individual tile's magnetization switches independently. In this last case, we have experimental access to the distribution of nucleation sites. Thus, we have found a clear signature of the magnetic interaction between patterned epitaxial micro tiles with in-plane magnetization. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 340-342 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Nanocrystallized cobalt clusters embedded in a copper matrix exhibiting giant magnetoresistance have been revealed by scanning force and friction microscopy. The microscopic images reported here should be important to understand the magnetic properties of these novel systems. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
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