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  • Articles  (65)
  • 1995-1999  (65)
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  • 1
    ISSN: 1573-4986
    Keywords: glycoprotein ; glycosylation ; gp120 ; HIV ; MALDI-TOF-MS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Neutral complex-type N-glycans of the envelope glycoprotein 120 of HIV-2, propagated in different host cells, display cell-type specific variations. In order to identify typical structural elements, glycans were analysed by gel filtration, by enzymic sequencing and, in part, by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The characteristic substituents of di- tri- and tetraantennary carbohydrate units thus observed include N-acetyllactosamine repeats, bisecting N-acetylglucosamine and fucose linked to the chitobiose core as well as to N-acetyllactosamine antennae. Each glycoprotein preparation displayed a characteristic set of glycoforms. Abbreviations: endo H, endo-β-N-acetylglucosaminidase H; E-PHA, Phaseolus vulgaris agglutinin E4; GlcNAcOH, N-acetyl-glucosaminitol; gp120/HUT78(MOLT4/Mφ/PBL/U937), external envelope glycoprotein 120 of HIV-2, strain D194, propagated in HUT78 (MOLT4, Mφ, PBL, U937) cells; gu, glucose units; HPAEC, high-pH anion-exchange chromatography; MALDI-TOF-MS, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry; Mφ, human monocytes/macrophages; PBL, human peripheral blood lymphocytes; PNGase F, peptide-N4-(N-acetyl-β-glucosaminyl)asparagine amidase F
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  • 2
    ISSN: 1573-515X
    Keywords: dissolved humic substances ; FTIR spectroscopy ; land use history ; peat ; synchronous fluorescence spectroscopy ; UV/VIS spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The elemental composition and spectroscopic properties of dissolved fulvic acids isolated from different sampling media (topsoil, ground and surface water) of a natural fen area (high portion of organic soils) were examined to reveal the effects of land use history. These effects need to be known if dissolved humic substances are to be a major factor in identifying the impact of present and future changes in land use. Dissolved fulvic acids (topsoil, groundwater) from highly degraded peatlands (due to a long-term agricultural use) exhibit lower C/N ratios, higher absorption in the UV spectra, and higher absorption at 1,620 cm−1 in the FTIR spectra compared with fulvic acids from relatively intact peatlands. These properties illustrate that long-term agricultural use with high inputs results in increased aromatic structures and a further humification of dissolved fulvic acids due to very strong peat decomposition compared with relatively intact peatlands. Synchronous fluorescence spectra also indicate the higher level of aromatic structures within fulvic acids isolated from sites with long-term agricultural use (high peat decomposition) compared with a land use history resulting in a lower peat decomposition. The different sources of fulvic acids in surface water (precipitation, runoff, interflow, groundwater) are the main reason for these effects not being detected in fulvic acids isolated from surface water. Short-term changes in land use characterized by a transition from crop farming to an unimproved grassland were found not to affect the spectroscopic properties of dissolved fulvic acids. A humification index deduced from the synchronous fluorescence spectra is proposed. We have strong evidence that dissolved humic substances indicate changes in the environmental conditions (both anthropogenic and natural) of wetlands with a high proportion of organic soils.
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  • 3
    ISSN: 1573-515X
    Keywords: dissolved humic substances ; FTIR spectroscopy ; land use history ; peat ; synchronous fluorescence spectroscopy ; UV/VIS spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The elemental composition and spectroscopic properties of dissolved fulvic acids isolated from different sampling media (topsoil, ground and surface water) of a natural fen area (high portion of organic soils) were examined to reveal the effects of land use history. These effects need to be known if dissolved humic substances are to be a major factor in identifying the impact of present and future changes in land use. Dissolved fulvic acids (topsoil, groundwater) from highly degraded peatlands (due to a long-term agricultural use) exhibit lower C/N ratios, higher absorption in the UV spectra, and higher absorption at 1,620 cm−1 in the FTIR spectra compared with fulvic acids from relatively intact peatlands. These properties illustrate that long-term agricultural use with high inputs results in increased aromatic structures and a further humification of dissolved fulvic acids due to very strong peat decomposition compared with relatively intact peatlands. Synchronous fluorescence spectra also indicate the higher level of aromatic structures within fulvic acids isolated from sites with long-term agricultural use (high peat decomposition) compared with a land use history resulting in a lower peat decomposition. The different sources of fulvic acids in surface water (precipitation, runoff, interflow, groundwater) are the main reason for these effects not being detected in fulvic acids isolated from surface water. Short-term changes in land use characterized by a transition from crop farming to an unimproved grassland were found not to affect the spectroscopic properties of dissolved fulvic acids. A humification index deduced from the synchronous fluorescence spectra is proposed. We have strong evidence that dissolved humic substances indicate changes in the environmental conditions (both anthropogenic and natural) of wetlands with a high proportion of organic soils.
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  • 4
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Gel permeation chromatography (GPC) was applied for recognizing the origin of groundwater humic and fulvic acids. GPC was performed with Fraktogel TSK HW-50 in 0.1 M NaCl, pH 8.5 (0.05 M phosphate buffer), 1 mM EDTA, with 10% by volume methanol added. Humic substances from groundwaters and sediments of four different aquifer systems in Germany were isolated, purified and characterized. Both UV/Vis and fluorescence detection were applied. UV/Vis detection was found to be more powerful in identifying differences between the various humic and fulvic acids. The four aquifer systems investigated (“Gorleben”, “Fuhrberg”, “Franconian Albvorland” and “Munich”) differed from one another with respect to hydrological and geochemical conditions. The results showed that the GPC-elution behavior reflects the geochemical environment and origin (source material and generation process) of aquatic humic and fulvic acids.
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  • 5
    ISSN: 1432-0916
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We present a direct approach for the calculation of functional determinants of the Laplace operator on balls. Dirichlet and Robin boundary conditions are considered. Using this approach, formulas for any value of the dimension,D, of the ball, can be obtained quite easily. Explicit results are presented here for dimensionsD=2,3,4,5 and 6.
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  • 6
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 7
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 8
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
    ISSN: 1573-904X
    Keywords: lipid vesicles ; nitrosourea ; medulloblastoma ; high-dose chemotherapy ; increased drug exposure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To reduce the systemic toxicity and prolong the systemic presence of l-(2-chloroethyl)-3-cyclohexyl-l-nitrosourea (CCNU), a lipid-based drug carrier was designed and characterized. Methods. The degree of CCNU association with lipid vesicles composed of 1,2-dimyristoyl-sn- glycero-3-phosphocholine (DMPC) and l,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) (1:1, m/m) was characterized and the drug decomposition rates of lipid-drug complexes were monitored. Effects of lipid association on drug potency against medulloblastoma cells and total systemic drug exposure in rats were determined. Results. At a CCNU:lipid molar ratio greater than 1:5, more than 90% of the drug was associated with the lipid vesicles. In aqueous suspensions, lipid association significantly reduced the first-order drug decomposition rate. In addition, lipid-associated CCNU exhibited a 4-fold increase in drug sensitivity with medulloblastoma cells. IC50 values for CCNU admixed and encapsulated with lipid vesicles were 18 ± 4.9 and 14.0 ± 2.2 μM, respectively, compared to 83 ± 11.0 μM for free CCNU. When administered to rats, lipid-associated CCNU increased the AUC (area under the concentration-time curve) of CCNU by approximately 2-fold (20.46 ± 2.15 compared to 39.59 ±1.87 μg⋅min/ml), and the terminal half-life (t1/2β) by almost 9-fold (17 ± 9 compared to 147 ± 48 min) over free CCNU. Despite the increase in total systemic drug exposure, rats treated with lipid-associated CCNU exhibited a significantly lower frequency of acute neurotoxicity. Conclusions. These data indicate that CCNU associated with lipid vesicles may increase drug stability, potency, and systemic exposure in rats.
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  • 10
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The immunoreactivity ofTaenia saginata andT. crassiceps metacestode neutral glyco(sphingo)lipids towards IgG antibodies derived from the sera of calves with experimental cysticercosis has been established. The glyco(sphingo)lipids are separable by normal-phase HPTLC (high-performance thin-layer chromatography) into groups of increasing sugar-chain length (lipid/ceramide mono-, di-, tri-, tetra- and 〉tetrasaccharides), with those corresponding to three and four hexoses being the main immunoreactive components (HPTLC immunostaining). In ELISA (enzyme-linked immunosorbent assay), reverse-phase HPTLC-isolatedT. crassiceps metacestode glyco(sphingo)lipids equivalent to tri- and tetrahexoside allowed a discrimination between non-infected and infected calves (at least 80 metacestodes recovered). The formation of IgG antibodies was correlated with the infection, not with other non-specific inducing factors, as seen by the differential humoral response detected in experimentally infected (T. saginata) calves before and after Praziquantel treatment (HPTLC immunostaining and ELISA).
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