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  • 1
    ISSN: 1617-4623
    Keywords: A-factor ; Streptomyces griseus ; Streptomycin biosynthesis ; Streptomycin resistance ; Gene expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A-factor (2-isocapryloyl-3R-hydroxymethyl-γ-butyrolactone) is a microbial hormone controlling streptomycin (Sm) production, Sm resistance and sporulation in Streptomyces griseus. In order to identify A-factor-dependent promoters in the Sm biosynthetic gene cluster, a new promoter-probe plasmid with a low copy number was constructed by using an extremely thermostable malate dehydrogenase gene as the reporter. Of the three promoters in the Sm production region that includes strR, aphD and strB, only the promoter of strR, which codes for a putative regulatory protein, was found to be directly controlled by A-factor. This was also confirmed by S1 nuclease mapping. The region essential for its A-factor-dependence was determined to be located 430–330 base pairs upstream of the transcriptional start point. Increase in the copy number of the strR promoter region did not lead to a corresponding increase in the total promoter activity, probably due to titration of a putative activator which binds to the enhancer-like region and controls the expression of the strR promoter. This putative activator is apparently distinct from the A-factor-receptor protein. The aphD gene, which encodes the major Sm resistance determinant, Sm-6-phosphotransferase, was transcribed mainly by read-through from the A-factor-dependent strR promoter; this accounts for the prompt induction of Sm resistance by A-factor.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Polymerisation von Methylmethacrylat wurde in Gegenwart von Cupra-rayon, Wasser und Tetrachlorkohlenstoff durchgeführt; sie verläuft radikalisch. Der Einfluß der zugesetzten Mengen an Monomerem, Cupra-rayon, Wasser oder Tetrachlorkohlenstoff auf die Polymerisationsgeschwindigkeit wurde untersucht, und aus den ermittelten Werten der Geschwindigkeiten wurde die Bruttoaktivierungsenergie im Temperaturbereich zwischen 70 und 90°C zu 9,7 kcal/Mol geschätzt. Weiter wurde gefunden, daß n-Butylacrylat sowie-methacrylat auch von dem oben erwähnten System polymerisiert werden, während Styrol und Acrylnitril sich nicht polymerisieren lassen.
    Notes: Polymerization of methyl methacrylate was carried out in the presence of cupra-rayon, water and carbon tetrachloride. It was concluded that the process was of radical mechanism. The effects of the amount of methyl methacrylate, cupra-rayon, water or carbon tetrachloride on the rate of polymerization were investigated. From the rates of polymerization at 70-90°C, overall activation energy was estimated as 9.7 kcal/mole. n-Butyl acrylate and methacrylate were also polymerized by the above system. However, styrene and acrylonitrile did not polymerize.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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