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  • 1995-1999  (4)
  • 1975-1979  (1)
  • silane  (2)
  • siloxanes  (2)
  • Clostridium acidiurici  (1)
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Material
Years
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Selenium requirement for active xanthine dehydrogenase from Clostridium acidiurici and Clostridium cylindrosporum (1979)
    Springer
    Archives of microbiology 121 (1979), S. 255-260 
    Details
    ISSN: 1432-072X
    Keywords: Purine fermentation ; Xanthine dehydrogenase ; Selenium ; Tungsten ; Molybdenum ; Clostridium acidiurici ; Clostridium cylindrosporum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The xanthine dehydrogenase of Clostridium acidiurici and C. cylindrosporum was assayed with methyl viologen as acceptor. In C. acidiurici the basal activity level was about 0.3 μmol/min x mg of protein. Cells grown on uric acid in the presence of 10-7 M selenite showed a 14-fold increase in xanthine dehydrogenase activity, which decreased with higher selenite concentrations (10-5 M). The supplementation with 10-7 M molybdate or tungstate was without effect. High concentrations of tungstate decreased the xanthine dehydrogenase if selenite was also present. In comparison, high concentrations of molybdate affected only a small decrease in activity level at the optimal concentration for selenite and relieved to some degree the inhibitory effect of 10-5 M selenite. With hypoxanthine and xanthine as substrates for growth again only the addition of selenite was necessary to show a similar increase in xanthine dehydrogenase activity. C. acidiurici could be grown in a mineral medium. Both xanthine dehydrogenase and formate dehydrogenase exhibited the highest level of activity if selenite and tungstate were present in that medium. In C. cylindrosporum the basal activity level of xanthine dehydrogenase was about 0.95 μmol/min x mg of protein. The addition of 10-7 M selenite to the growth medium increased the activity level about 3-fold, but the highest level (3.7 U/mg) was reached if 10-7 M molybdate was also added. The presence of tungstate resulted in a decreased enzyme activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00425064
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Silicon-Modified Carbohydrate Surfactants I: Synthesis of Siloxanyl Moieties Containing Straight-chained Glycosides and Amides (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 10 (1996), S. 421-435 
    Details
    ISSN: 0268-2605
    Keywords: siloxanes ; carbohydrate modified ; surfactants ; saccharide ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New siloxanyl-modified carbohydrate surfactants of the amide and glycoside type have been synthesized by coupling between defined as well as higher-molecular-weight siloxanes and carbohydrate structures via spacers of different lengths and hydrophilic power. Linear and branched monohydrogen di-, tri-, tetra- and penta-siloxanes and polyhydrogen siloxanes as well as mono- and di-saccharide lactone structures have been found to be good starting materials for the synthesis of amides, often in quantitative yield, whereas glycosides had to be prepared in low-yield multistep sequences including protection/deprotection steps. Selected strategies were applied to polysiloxanes yielding quantitatively a broad variety of carbohydrate-modified comb-like structures. The new substances were characterized by means of 13C NMR spectroscopy, GC, capillary GC, GC-MS coupling and elemental analysis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 3
    Electronic Resource
    Electronic Resource
    Silicon-Modified Carbohydrate Surfactants II: Siloxanyl Moieties Containing Branched Structures (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 10 (1996), S. 437-450 
    Details
    ISSN: 0268-2605
    Keywords: siloxanes ; surfactant ; carbohydrate ; amino ; regioselective ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Branched siloxanyl-modified carbohydrate surfactants have been synthesized by coupling mono-, di- and poly-functional siloxanes to carbohydrate units either via a branched spacer or by attaching a separate modifying element to a straight-chained structure. Hydrophilic as well as extremely hydrophobic elements have been incorporated successfully. Siloxanyl-modified carbohydrates bearing a secondary amino function were alkylated in regioselective reactions by different epoxides ranging from glycidol- to siloxanyl-modified allyl glycidyl ether derivatives. Alternatively, carbohydrate-modified piperazinyl structures yielded cyclic subunits after alkylation. Structures bearing two identical hydrophilic groups are accessible by alkylation of carbohydrate-modified bisamides. The derivatives synthesized were characterized by means of GC, NMR and elemental analysis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Silicon-modified carbohydrate surfactants VI: Synthesis of carbosilane, silane, polysilane and non-permethylated siloxane derivatives; the wetting behaviour of epoxy-modified precursor liquids on non-polar surfacesIn remembrance of Professor Dr Edwin Hengge (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 47-58 
    Details
    ISSN: 0268-2605
    Keywords: surfactants ; carbohydrate ; carbosilane ; silane ; wetting ; surface tension ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of carbohydrate surfactants bearing carbosilane, silane, polysilane and non-permethylated siloxane moieties is described. These surfactants consist of three structural elements: (1) a silicon-containing moiety, (2) a spacer and (3) a carbohydrate unit. Additionally two different types of mixed structures have been synthesized: (a) single-chained carbosilane-siloxane surfactants and (b) double-chained combinations of carbo- silanes, silanes and siloxanes. The wetting behaviour of the key intermediates, the allyl glycidyl derivatives, has been investigated by static surface tension (γlv, σ) and wetting tension (γsv-γsl, α) measurements on a non-polar perfluorinated surface (FEP® plate). The contact angles obtained for these pure liquids are not a linear function of the surface tension but depend on the polarity of the substructures. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 5
    Electronic Resource
    Electronic Resource
    Silicon-modified carbohydrate surfactants. VII: Impact of different silicon substructures on the wetting behaviour of carbohydrate surfactants on low-energy surfaces  -  distance decay of donor-acceptor forces (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 265-276 
    Details
    ISSN: 0268-2605
    Keywords: carbohydrate surfactants ; wetting behaviour ; siloxane ; silane ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The wetting behaviour of carbohydrate surfactants bearing siloxane, carbosilane, polysilane or silane moieties has been investigated. By static surface tension (γlv, σ) and wetting tension (γsv-γsl, α) measurements on a non-polar perfluorinated surface (FEP®), the contact angles of aqueous surfactant solutions above the critical micelle formation concentration (cmc) were determined. Surface tension and wetting tension react independently on defined changes in the chemical structure of the surfactant molecules. Siloxane surfactants reduce the surface tension most effectively, whereas for a neopentyl-substituted silane derivative the lowest solid/liquid interfacial tension was found. The data for isomeric siloxanes, carbosilanes and silanes suggest that donor-acceptor forces at solid interfaces have a maximum range of about 4.5 Å. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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