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  • Articles  (9)
  • Analytical Chemistry and Spectroscopy  (7)
  • Geophysics
  • METEOROLOGY AND CLIMATOLOGY
  • Models, Molecular
  • ddc:330
  • 1995-1999  (5)
  • 1985-1989  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Thermospray mass spectroscopy/high performance liquid chromatographic identification of the metabolites formed from arteether using a rat liver microsome preparation (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 18 (1989), S. 337-351 
    Details
    ISSN: 0887-6134
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thermospray LC/MS methods with internal standardization were developed for the quantification of the antimalarial arteether and six of its metabolites at the 1-10 μg/ml level in liver microsome preparations without the use of solvent extraction. The thermospray mass spectra of arteether and most of its metabolites exhibited strong [M + NH4]+ and [M - OR]+ peaks arising from the molecular ion adduct and the loss of the alkoxy or hydroxy group of the side chain. In addition to the six metabolites for which authentic reference standards were available, three additional metabolites were detected. The major metabolites of arteether were found to be dihydroartemisinin, deoxydihydroartemisinin, 3-hydroxydeoxydihydroartemisinin, two isomers of hydroxyarteether, and 3-hydroxydeoxyarteether. Deoxyartheether was not found at significant concentrations in the microsome preparation.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200180509
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  • 2
    Electronic Resource
    Electronic Resource
    Octafluorotoluene as a derivatizing agent for steroids in human plasma (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 211-213 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of octafluorotoluene (OFT) as a versatile gas chromatographic/mass spectrometric derivatizing agent for steroids containing alcoholic, phenolic or α,β-unsaturated keto functions, is described. Two distinct derivatizing schemes can be utilized, involving (method 1) a phase-transfer reaction, employing a two-phase system of CH2Cl2 and N NaOH with n-Bu4NHSO4 as catalyst (suitable for alcoholic and phenolic steroids) and (method 2) a reaction conducted in anhydrous dimethylformamide at 155°C with CsF as base (appropriate for α,β-unsaturated keto steroids). Perfluorotolyl (PFT) ethers and/or enol ethers have thus been generated. The electron impact spectra display abundant high-mass molecular ions where derivatization has occurred at a phenolic or enolic function. An extraction, derivatization and gas chromatographic/mass spectrometric scheme has been devised involving method 2 for the analysis of steroids in human plasma. A preliminary quantitative investigation of the levels of testosterone in plasma has been carried out employing these methods. The anomalously high level found is explained in terms of the presence in plasma of lipid-soluble derivatives of testosterone (probably fatty acid esters) which generate the testosterone bis-OFT derivative under the reaction conditions employed.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160138
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  • 3
    Electronic Resource
    Electronic Resource
    Modified ionspray interface for supercritical fluid chromatography/mass spectrometry: Interface design and initial results (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1087-1094 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A pneumatically assisted electrospray liquid chromatography/mass spectrometry interface has been modified for use with open-tubular supercritical fluid chromatography (SFC). The modified interface houses the SFC flow restrictor within the spray device. A sheath-flow liquid of methanol or methanol/water containing ammonium acetate flows coaxially to the restrictor. The addition of the sheath-flow liquid results in the ionization of analytes known to be in a neutral charge state during the chromatographic separation. The sheath-flow liquid also allows for the independent operation of the chromatograph and the mass spectrometer. Both could be operated under optimum conditions. The operation of the interface was optimized using a solution of poly(dimethylsiloxane) in CO2 introduced by continuous infusion. We also report the application of the modified instrument to samples containing amines and propoxylated alcohols.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091202
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  • 4
    Electronic Resource
    Electronic Resource
    Development and application of a gas chromatographic/mass spectrometric/mass spectrometric method for the determination of 5-methoxyflavone in rat and dog plasma (1995)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 30 (1995), S. 438-445 
    Details
    ISSN: 1076-5174
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A gas chromatographic/mass spectrometric/mass spectrometric method was developed for the determination of 5-methoxyflavone in plasma. Optimized detection schemes for 5-methoxyflavone readily allow a limit of quantification of 1 ng ml-1 in rat or dog plasma (1.0 ml sample volume). The complete analysis time (injection to injection) is less than 9 min and allows for rapid automated sample throughput. Additional advantages include a high degree of specifity and good accuracy and precision. This type of rapid tandem mass spectrometric assay has been found to be particularly useful in pharmaceutical discovery, since an assay for one compound can be quickly developed, utilized and then modified to determine analogs of similar structure. Application of this methodology to pilot preclinical pharmacokinetic studies of the drug indicated that it is rapidly absorbed and cleared, with an apparent terminal half-life of about 15 min in dogs. Bioavailability in the two dogs tested ranged 33 to 72%, but was about 25% in rats.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jms.1190300307
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  • 5
    Electronic Resource
    Electronic Resource
    Mass spectrometry of pancuronium bromide and related quaternary ammonium steroids using the moving belt LC/MS interface (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 24 (1989), S. 723-732 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pancuronium and vecuronium are members of a series of quaternary ammonium steroids used as neuromuscular blocking agents in anesthesiology. In this study the mass spectrometric properties of these bromide salts are examined and spectral features which permit their differentiation are evaluated. The relative merits of chemical ionization and fast atom bombardment using the moving belt liquid chromatography/mass spectrometry interface have been investigated. Fragmentation pathways for both ionization methods were determined with deuterium labeling and linked-scan techniques. Cleaner spectra can be obtained via the matrix-free belt introduction system as compared to conventional fast atom bombardment.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210240904
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  • 6
    Electronic Resource
    Electronic Resource
    Mass spectrometry of basic aluminum sucrose octasulfate using fast atom bombardment with a saturated tetramethylammonium ion sample matrix (1989)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 24 (1989), S. 895-897 
    Details
    ISSN: 0030-493X
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A fast atom bombardment method to produce stable molecular cations of sucrose octasulfate8- is described. The technique centers on ion exchange of the nonvolatile inorganic aluminum hydroxide cations for more volatile organic tetramethylammonium ions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/oms.1210241008
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  • 7
    Electronic Resource
    Electronic Resource
    Raman, infrared and 13C NMR studies of mixed halides of cyclopropene, C3ClnBr4 - n, and cyclopropane, C3ClnBr6 - n (1995)
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 26 (1995), S. 595-599 
    Details
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Tetrachlorocyclopropene, C3Cl4, is converted into C3Br4 by treatment with BBr3. Use of less than the stoichiometric amount of BBr3 leads to mixed halides C3ClnBr4-n which are identified and investigated by Raman and 13C NMR spectroscopy. The addition of Br2 to C3Cl4 yields both the isomers cis- and trans-1,2-dibromotetrachlorocyclopropane in equal quantities; the vibrational spectra are reported and partially assigned. Raman and 13C NMR of other mixed halides of cyclopropane, C3ClnBr6-n are discussed. A 35Cl/37Cl isotope effect is detected on the carbon chemical shift of C3Cl6 I2 fails to react with C3Cl4 or C3Br4.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jrs.1250260803
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  • 8
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    A mechanism of drug action revealed by structural studies of enoyl reductase (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-12-20
    Description: Enoyl reductase (ENR), an enzyme involved in fatty acid biosynthesis, is the target for antibacterial diazaborines and the front-line antituberculosis drug isoniazid. Analysis of the structures of complexes of Escherichia coli ENR with nicotinamide adenine dinucleotide and either thienodiazaborine or benzodiazaborine revealed the formation of a covalent bond between the 2' hydroxyl of the nicotinamide ribose and a boron atom in the drugs to generate a tight, noncovalently bound bisubstrate analog. This analysis has implications for the structure-based design of inhibitors of ENR, and similarities to other oxidoreductases suggest that mimicking this molecular linkage may have generic applications in other areas of medicinal chemistry.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Baldock, C -- Rafferty, J B -- Sedelnikova, S E -- Baker, P J -- Stuitje, A R -- Slabas, A R -- Hawkes, T R -- Rice, D W -- New York, N.Y. -- Science. 1996 Dec 20;274(5295):2107-10.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Sheffield S10 2TN, UK. D.Rice@sheffield.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8953047" target="_blank"〉PubMed〈/a〉
    Keywords: Anti-Bacterial Agents/*metabolism/pharmacology ; Binding Sites ; Boron Compounds/*metabolism/pharmacology ; Crystallography, X-Ray ; Drug Design ; Drug Resistance, Microbial ; Enoyl-(Acyl-Carrier-Protein) Reductase (NADH) ; Enzyme Inhibitors/*metabolism/pharmacology ; Escherichia coli/enzymology ; Escherichia coli Proteins ; Fatty Acid Synthase, Type II ; Fatty Acid Synthases/antagonists & inhibitors/*chemistry/metabolism ; Hydrogen Bonding ; Models, Molecular ; NAD/*metabolism ; Oxidoreductases/antagonists & inhibitors/*chemistry/metabolism ; Protein Conformation ; Protein Structure, Secondary
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Crystal structure of DNA recombination protein RuvA and a model for its binding to the Holliday junction (1996)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 1996-10-18
    Description: The Escherichia coli DNA binding protein RuvA acts in concert with the helicase RuvB to drive branch migration of Holliday intermediates during recombination and DNA repair. The atomic structure of RuvA was determined at a resolution of 1.9 angstroms. Four monomers of RuvA are related by fourfold symmetry in a manner reminiscent of a four-petaled flower. The four DNA duplex arms of a Holliday junction can be modeled in a square planar configuration and docked into grooves on the concave surface of the protein around a central pin that may facilitate strand separation during the migration reaction. The model presented reveals how a RuvAB-junction complex may also accommodate the resolvase RuvC.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Rafferty, J B -- Sedelnikova, S E -- Hargreaves, D -- Artymiuk, P J -- Baker, P J -- Sharples, G J -- Mahdi, A A -- Lloyd, R G -- Rice, D W -- Wellcome Trust/United Kingdom -- New York, N.Y. -- Science. 1996 Oct 18;274(5286):415-21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Krebs Institute, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK. d.rice@sheffield.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/8832889" target="_blank"〉PubMed〈/a〉
    Keywords: Bacterial Proteins/*chemistry/metabolism ; Base Composition ; Crystallography, X-Ray ; DNA Helicases/metabolism ; DNA, Bacterial/chemistry/*metabolism ; DNA-Binding Proteins/*chemistry/metabolism ; Endodeoxyribonucleases/metabolism ; Escherichia coli ; *Escherichia coli Proteins ; Hydrogen Bonding ; Models, Molecular ; *Nucleic Acid Conformation ; Oligodeoxyribonucleotides/chemistry/metabolism ; *Protein Conformation ; Protein Structure, Secondary ; Protein Structure, Tertiary ; *Recombination, Genetic
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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