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  • solubilization  (4)
  • False positives  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Mutagenicity testing with Salmonella microsome test (1980)
    Springer
    Archives of toxicology 46 (1980), S. 31-40 
    Details
    ISSN: 1432-0738
    Schlagwort(e): Ames test ; Plate incorporation assay ; Salmonella/microsome test ; Test procedure ; False negatives ; False positives
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract This in vitro mutagenicity test system comprises five different strains of S. typhimurium as target cells with the rat liver S-9 fraction and appropriate co-factors for metabolic activation of the chemical tested. The bacterial tester strains detect both mutations induced by base pair substitutions and intercalation (frame shift mutations). Usually 108–109 cells of an overnight culture or an exponentially growing culture are incubated for 2–3 days with a mixture of S-9, co-factors, soft agar and the chemical on histidine-deficient agar. The S-9 fraction is obtained from the livers of rats pretreated with 500 mg/kg chlorinated biphenyls (Clophen A-50, Aroclor 1254) to obtain high metabolic activity. For reproducibility it is essential to standardize metabolic activity and protein content of the S-9 and to use three different concentrations thereof in the test system. Since solvents inhibit metabolic activation of the chemicals they must not exceed 4% of the final 2.6 ml incubate. Several independent studies have shown that between 85 and 93% of chemical carcinogens are mutagens in the test. Regarding extrapolation to man one has to consider that the test is preferentially adapted for metabolic activation of the chemicals, whereas inactivation processes are absent or are less active than in vivo. Thus, the test provides qualitative rather than quantitative information on mutagenic effects of a chemical.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00361243
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  • 2
    Digitale Medien
    Digitale Medien
    Influence of solubilized stilbene derivatives intrans andcis configuration on the phase equilibrium hexagonal —isotropic in potassium octanoate —water systems: Light-induced isothermal switching of clearing points (1996)
    Springer
    Colloid & polymer science 274 (1996), S. 904-907 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Lyotropic liquid crystals ; phase transitions ; photoisomerization ; solubilization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Clearing temperaturesT HI, as observed in phase transitions from the hexgonal lyotropic liquid crystalline phase to the isotropic micellar phase of aqueous potassium octanoate systems were found to be sensitive to the presence of small amounts of certain stilbene derivatives. The influence onT HI is specific for the stilbene derivative and depends on whether thecis ortrans form is present. Sincetrans andcis isomers can be interconverted photochemically, phases can be switchedin situ upon exposure to light. Eight derivatives of stilbene were tested: 4-hydroxystilbene, 4-potassium-stilbenolate, 3− and 4-carboxystilbene, 3- and 4-potassium stilbene carboxylate, 2′,5′-dimethoxy-4-aminostilbene, and 4,4′-diaminostilbene-2,2′-disulfonic acid. Upon solubilizing ≤1% w/w of trans stilbenes the clearing points varied between +15.5 K to −12 K as compared to pure aqueous potassium octanoate. Photoisomerization to the cis form resulted in increases ofT HI by up to 7.5 K.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00654751
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  • 3
    Digitale Medien
    Digitale Medien
    Micellization of cetyltrimethylammonium bromide in the presence of 9-anthryl alkanols (1997)
    Springer
    Colloid & polymer science 275 (1997), S. 850-859 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Key words Surfactants ; micellization ; solubilization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract  Surface tension measure-ments in aqueous cetyltrimethyl ammonium bromide were performed in presence of various amounts of 9-(hydroxymethyl)anthracene (AM), 9-[1-(1-hydroxy)ethyl]anthracene (THAE), and 9-[1-(1-hydroxy-2,2,2-trifluoro)ethyl]anthracene (TFAE). Free energies ΔG ⊖ m and ΔG ⊖ i of micellization and of adsorption to the air–water interface, respectively, were determined as well as the corresponding enthalpies and entropies. ΔG o− m of micellization increased in the presence of AM and THAE, but became more negative when TFAE was added. In contrast to AM and THAE, TFAE addition decreases ΔS ⊖ i. For this peculiarity of TFAE, its location and orientation in micellar solution was investigated by means of UV and 19F-NMR spectroscopy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003960050157
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  • 4
    Digitale Medien
    Digitale Medien
    Rheological and photorheological effects in aqueous solutions of cetyltrimethylammonium bromide containing 9-anthrylalkanols (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 1222-1231 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Light scattering ; micelles ; rheology ; photochemistry ; solubilization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Viscosities, flow properties, and static low-angle light scattering of dilute (≤250 mmol/dm3) aqueous micellar solutions of cetyltrimethylammonium bromide were measured in the presence of various amounts of 9-anthrylmethanol (AM), 2,2,2-trifluoro-1-(9-anthryl)ethanol (TFAE), 1-(9-anthryl)ethanol (AE), 9-methylanthracene (MA), and 9-ethylanthracene (EA). At room temperature the solubilization of AM induces an increase of viscosity and a rise in aggregation numbers (as determined from low-angle light scattering). Both features are reverted upon in in situ photodimerization of AM. After lowering the temperaure, non-Newtonian flow is detected by means of a rotating viscometer. The solubilization of AE and EA, respectively, leads to analogous observations, while no viscoelastic features were obtained with solubilized MA. TFAE containing systems at room temperature show non-Newtonian flow accompanied by viscoelasticity which can be ascribed to the formation of long rod-like micelles. Raising the temperature as well as photodimerization diminish the lengths of the micelles and the non-Newtonian features.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01095063
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  • 5
    Digitale Medien
    Digitale Medien
    On the shape of giant micelles in aqueous solutions of cetyltrimetylammoniumbromide (CTAB) (1992)
    Springer
    Colloid & polymer science 270 (1992), S. 822-824 
    Details
    ISSN: 1435-1536
    Schlagwort(e): Low-temperature electronmicroscopy ; shape ofmicelles ; solubilization ; cetyltrimethylammonium bromide ; N-methyl-N,N-diphenylamine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau
    Notizen: Abstract Low-temperature electron microscopy was used to image fracture faces of shock-frozen aqueous solutions containing the very large micelles of CTAB existing in the presence of N-methyl-N,N-diphenylamine (MDPA) and 9-anthracene carboxylic acid (9-AC) as solubilizates. When MDPA is present, large globular micelles are formed which have total aggregation numbers of the order of 105 and are seen to be clusters of smaller disc-like structures containing some thousand CTAB-units. Thread-like features are visualized in solutions containing 9-AC which is known to induce the formation of micellar rods.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00776154
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