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  • 1
    ISSN: 1520-6025
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1335
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Die Tatsache, daß die Leberzellen stärker durch Inkorporation von 3H-Aflatoxin markiert werden als die Mesenchymzellen entspricht der Beobachtung, daß Leberzellen gegenüber Aflatoxinen anfälliger sind als die Mesenchymzellen. Es zeigten sich keine signifikanten Unterschiede hinsichtlich der Inkorporation von 3H-Aflatoxin B 1, B 2 und 4HB 1 in die Leberzellen, während diese drei Mycotoxine eine weite Variation hinsichtlich ihrer Hemmwirkung auf die RNS-Synthese aufwiesen. Man kann also daraus den Schluß ziehen, daß die Toxizität von Aflatoxinen für Leberzellen in vitro eng zusammenhängt mit der Membrandurchlässigkeit und dem aktiven Teil des Aflatoxinmoleküls bzw. der Dop pelbindung in Difuranstruktur und der Carbonylgruppe in dem Cyclopentenon-Anteil von B 1.
    Notes: Summary The distribution patterns of 3H-aflatoxin B 1, B 2 and tetrahydrodesoxoaflatoxin B 1 (4H B 1) in the cultured liver cells originated from the 12-day-old chicken embryo were demonstrated. The fact that the hepatocytes were more heavily labeled than the mesenchymal cells by the incorporation of 3H-aflatoxins correlate well with the observation that the hepatocytes were more susceptible than the mesenchymal cells to the aflatoxins. There were no significant differences in the pattern of incorporation of 3H-aflatoxin B 1, B 2 and 4H B 1 into the hepatocyte, while the three mycotoxins show a wide variation in their inhibitory action in RNA synthesis. It may be concluded from the above mentioned facts that the toxicity of aflatoxins to the liver cells in vitro is closely related to the membrane permeability and the active portion of the molecule of aflatoxins, such as the double bond in the difuran structure and the carbonyl group in the cyclopentenone portion of B 1.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Quadratic electro-optic effects (dc or low frequency Kerr effect) of bacteriorhodopsin dispersed in dried gelatin thin films are examined in the near resonance region at three wavelengths: 633, 647, and 676 nm. The films show relatively large quadratic electro-optic effects compared to other molecular dispersed systems. The purple membrane is fixed within the polymerized gelatin matrix, and we show that the electronic contribution to γ dominates over possible orientational contributions. At 676 nm, the quadratic electro-optic coefficient s1133(−ω;0,0,ω) is 6.7×10−20 m2/V2 and the third order nonlinear susceptibility χ1133(3)(−ω;0,0,ω) is 7.0×10−13 cm4 statCoulomb−2, with both values obtained for a protein concentration of 6.9×1018 cm−3. The orientationally averaged second molecular hyperpolarizability 〈γ(−ω;0,0,ω)〉 determined from the quadratic electro-optic coefficients at 676 nm assuming an Onsager ellipsoidal local field factor is (10.8±5.1)×10−32 cm7 statCoulomb−2 [(1.34±0.63)×10−56 F3 m4 C−2]. The 〈γ(−ω;0,0,ω)〉 value increases roughly tenfold when the probe wavelength is decreased to 633 nm. The behavior of γ(−ω;0,0,ω), when fit to a two-state model, predicts that γ(−ω;0,0,ω) is strongly enhanced via type III processes. Thus, the magnitude of γ(−ω;0,0,ω) is dominated by a term (Δμ102×μ102)/(ω10−ω)3, where Δμ10 is the change in dipole moment, μ10 is the transition moment, and ω10 is the transition energy of the lowest-lying allowed 1Bu*+-like π,π* state. We calculate that Δμ10 is 12.8±1.2 D, in good agreement with previous Stark and two-photon experimental values. Time-dependent Hartree–Fock methods based on the MNDO Hamiltonian yield reasonable agreement with experiment, underestimating γ(−ω;0,0,ω) by factors of only 2–4, with the error increasing as the frequency approaches resonance. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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