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  • 1995-1999  (4)
  • 1
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A new family of homologous membrane proteins that transport galactosides–pentoses–hexuronides (GPH) is described. By analysing the aligned amino acid sequences of the GPH family, and by exploiting their different specificities for cations and sugars, we have designed mutations that yield novel insights into the nature of ligand binding sites in membrane proteins. Mutants have been isolated/constructed in the melibiose transport proteins of Escherichia coliKlebsiella pneumoniae and Salmonella typhimurium, and the lactose transport protein of Streptococcus thermophilus which facilitate uncoupled transport or have an altered cation and/or substrate specificity. Most of the mutations map in the amino-terminal region, in or near amphipathic α-helices II and IV, or in interhelix-loop 10–11 of the transport proteins. On the basis of the kinetic properties of these mutants, and the primary and secondary structure analyses presented here, we speculate on the cation binding pocket of this family of transporters. The regulation of the transporters through interaction with, or phosphorylation by, components of the phosphoenolpyruvate:sugar phosphotransferase system is also discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1436-5073
    Keywords: holmium ; derivative spectra ; 2-diphenylacetyl) indan 1,3-dione
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The zero-order and second-order derivative absorption spectra of the system of holmium with 2-(diphenylacetyl) indan-1, 3-dione and octylphenyl poly(ethyleneglycol) ether have been determined by derivative spectrophotometry. The molar absorptivity of absorption spectra and the derivative spectra are calculated respectively. The absorbances at the absorption maxima for the holmium complex are 48.5 (at 450 nm) and 14.5 (at 460 nm) times greater than for the corresponding chloride. The derivative spectra have been used to eliminate the interference of other lanthanides, and the sensitivity is again increased by a factor of about 5. The calibration graph is linear up to ∼ 25 μg/ml of holmium. The detection limit, obtained from the sensitivity of the calibration graph and for 3S b (Sb = standard deviation of a blank without holmium,n = 11), was 0.37 μg/ml of holmium. The quantification limit (10Sb was 1.2 μg/ml. The method has been applied successfully to synthetic and reference samples of rare earths.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract O1 hybridoma cells, which secrete an IgM antigalactocerebroside, were implanted into the spinal cord of cyclosporine-treated juvenile or adult rats, and the animals were sacrificed ∼2–3 wk later. About half the recipient animals developed myelin lesions. In some, sharply circumscribed foci of demyelination formed within the dorsal columns. Cellular reaction consisted of macrophages containing refractile globules in the parenchyma and within enlarged perivascular spaces as well as thickened endothelial cells. “Shadow plaques” also developed, i.e. regions in which axons were surrounded by thin myelin sheaths, compatible with remyelination. In addition, we found damaged axons, some of which were swollen with organelles, comparable to the enlarged axon profiles seen at sites of constriction or interruption. Compromise of the blood-brain barrier at sites of hybridoma growth was demonstrated by extravasation of Evans blue dye. Discontinuation of cyclosporine was followed by an anti-hybridoma, complement-fixing antibody response within 2–3 d. This model of focal CNS demyelination and remyelination, with evidence of some axon damage, is mediated by a defined IgM antiglycolipid monoclonal antibody secreted within the spinal cord parenchyma. The lesions, which are similar to those of multiple sclerosis, probably result from the interaction between the intrathecally secreted IgM antibody and complement entering from the circulation at foci of compromised blood-brain barrier plus activation of endogenous or hematogenous macrophages via their complement receptors.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of low temperature physics 105 (1996), S. 1273-1278 
    ISSN: 1573-7357
    Keywords: 74.20.−z ; 74.65.+n ; 74.60.Mj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Interlayer coupling in Bi2Sr2CaCu2O8+δ is studied with the out-of-plane resistance, R, in magnetic field, H, parallel to (ab)-plane of a crystal. Novel phenomenon manifesting itself by a sharp hysteretic jump in the tail of R(T, H) curve is observed at5.5 ≤ H ≤ 11T. Effect is entirely wiped out by a minor inclination from H ∥ (ab) orientation and presumably might be related with a first-order phase transition in the Josephson vortex system.
    Type of Medium: Electronic Resource
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