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  • A-factor  (1)
  • Immunofluorescence  (1)
  • Polymer and Materials Science  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Planta 197 (1995), S. 289-295 
    ISSN: 1432-2048
    Keywords: Chromatin ; Generative nucleus ; Histone variants ; Immunofluorescence ; Lilium ; Pollen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two proteins that resemble core histones and might be specific to the male gametic (generative) nucleus within the pollen of Lilium longiflorum Thumb, (originally designated p22.5 and p18.5; K. Ueda and I. Tanaka, 1994, Planta, 192, 446–452) were characterized biochemically and immunochemically. Patterns of digestion of p22.5 and p18.5 by Staphylococcus aureus V8 protease closely resembled those of somatic histones H2B and H3, respectively. However, peptide fragments that were unique to p22.5 or p18.5 were also detected. Antibodies raised against these proteins did not cross-react with any somatic histones. These results indicate that p22.5 and p18.5 are different from somatic histones in terms of primary structure. Analysis of their amino-acid compositions revealed that p22.5 is a moderately lysine-rich protein while p18.5 is an arginine-rich protein. From these results, we conclude that p22.5 is a variant of histone H2B and p18.5 is a variant of histone H3. Immunofluorescence staining of pollen grains using the specific antibodies revealed that both p22.5 and p18.5 are only present in the generative cell nucleus and are not to be found in the vegetative cell nucleus. This study demonstrates that (i) specific histone variants are present in the male gametic nucleus of a higher plant, as they are in the sperm nucleus of animals, and (ii) distinct differences in histone composition exist between the nuclei of generative and vegetative cells in pollen. These novel histones (p22.5 and p18.5), specific to male gametic nuclei, have been designated gH2B and gH3, respectively.
    Type of Medium: Electronic Resource
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  • 2
    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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  • 3
    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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