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  • Artikel: DFG Deutsche Nationallizenzen  (6)
  • 1-butene  (2)
  • CRABP-I  (2)
  • Malaria  (2)
  • 1
    ISSN: 1572-879X
    Schlagwort(e): 1-butene ; skeletal isomerization ; fluorine-modified alumina ; acid site concentration ; monomolecular reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract γ-alumina catalysts modified with different weight loadings of fluorine have been used for skeletal isomerization of 1-butene in order to investigate the effects of the fluorine loading level on the conversion of 1-butene and the selectivity to isobutene formation. Increasing the actual loading of fluorine up to 0.012 wt% led to an increase in conversion of 1-butene over fluorine-modified γ-alumina catalysts, while the high selectivity to isobutene remains almost unchanged. On the other hand, a clear trend of increasing 1-butene conversion with a decreasing selectivity to isobutene is observed for the γ-alumina catalysts with higher loadings of fluorine. An analysis of the results from the thermal analysis, NH3 temperature-programmed desorption, infrared and the 1-butene sorption measurments clearly indicates that the number of strong acid sites in the modified γ-alumina catalysts is greatly enhanced at fluorine loadings higher than 0.012 wt%, leading to the acceleration of 1-butene oligomerization followed by cracking to light hydrocarbons. Therefore, the 1-butene isomerization selectivity from fluorine-modified γ-alumina catalysts can be understood in terms of a competition between the monomolecular and bimolecular reaction pathways, which highly depend on the concentration of strong acid sites.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 57 (1999), S. 209-215 
    ISSN: 1572-879X
    Schlagwort(e): 1-butene ; skeletal isomerization ; mesoporous material ; acid site concentration ; monomolecular reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract On the skeletal isomerization of 1-butene, mesoporous materials with mesopores too large to expect any shape selectivity have been used in order to investigate the effects of the concentration of acid sites on the conversion of 1-butene and the selectivity for isobutene. The concentrations of acid sites can be varied through the control of the Si/Al ratio. The conversion of 1-butene increases with increasing the aluminium content of mesoporous materials, while the selectivity for isobutene decreases. The results of ammonia TPD, IR measurement of 1-butene adsorption, and TG analysis of used catalysts indicate that distant location of activated 1-butene molecules induces the monomolecular reaction over the mesoporous materials with low aluminium content, resulting in high selectivity for skeletal isomerization. On the mesoporous material with high aluminium content, however, the high concentration of activated 1-butene molecules accelerates the multimolecular oligomerization and, thus, reduces the selectivity.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 48 (1995), S. 65-69 
    ISSN: 1432-1041
    Schlagwort(e): Paracetamol ; Malaria ; pharmacokinetics ; phase II conjugation ; glucuronidation ; sulphation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Investigations in animals have suggested that conjugation of paracetamol may be reduced in malaria. We have measured plasma concentrations and the urinary excretion of paracetamol and its phase II metabolites in eight Thai patients during uncomplicated falciparum malaria and in convalescence, following a 1000 mg single oral dose. The apparent oral clearance (Malaria, 3.6; Convalescence, 3.9; ml·min−1·kg−1), the elimination half-life (Malaria, 3.8; Convalescence, 3.7 h) and apparent volume of distribution (Malaria, 1.2; Convalescence, 1.2; l·kg−1) of paracetamol were similar during malaria and convalescence. In addition, the urinary excretion of paracetamol and its major phase II metabolites and their formation clearances from paracetamol were not significantly different between the two study phases. These data show that clinical malaria infection has no effect on the conjugation of paracetamol in man.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    European journal of clinical pharmacology 49 (1996), S. 497-501 
    ISSN: 1432-1041
    Schlagwort(e): Quinine ; Malaria ; pharmacokinetics ; chronic renal failure
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Medizin
    Notizen: Abstract Methods: We investigated the pharmacokinetics of quinine (Qn) following administration of a single oral dose of 600 mg Qn sulphate in six male Thai patients with a moderate degree of chronic renal failure (CRF), and six male Thai subjects with normal renal function. Results: The drug was well tolerated in both groups of subjects; no major adverse reactions were observed. A marked alteration in the pharmacokinetics of Qn was found in patients with CRF compared to healthy subjects; there were six signifiicant changes in the pharmacokinetic parameters. Absorption was delayed, but increased in CRF (tmax 4.5 vs 1.6 h, Cmax 6.17 vs 3.45 μg·ml−1). Total clearance was significantly reduced 0.94 vs 2.84 ml·min−1·kg−1, whereas Vz/f remained unchanged (1.82 vs 2.78 1·kg−1). This resulted in the increased values of AUC and prolongation of the t1/2z and MRT in the patients (AUC 181.5 vs 61.8 μg·min−1·ml−1, t1/2z 26 vs 9.7 h, MRT 36.4 vs 11.3 h). Median concentrations of plasma unbound fraction of Qn collected at 4 h after drug administration in patients and healthy subjects were 7.3 vs 9.8%, respectively.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Molecular and cellular biochemistry 200 (1999), S. 69-76 
    ISSN: 1573-4919
    Schlagwort(e): CRABP-I ; RA induction ; RA binding ; mutagenesis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie , Medizin
    Notizen: Abstract We have mutated the type I cellular retinoic acid binding protein (CRABP-I), individually at the Arg131 (into Ala) and the Tyr 133 (into Phe) residues which have been predicted to make direct contact with retinoic acid (RA) based upon previous structural studies. The RA-binding affinities of these mutants are examined and their biological effects on RA induction of reporter genes are determined. The R131A mutation drastically affects its ligand-binding property, but the Y133F mutation has little effect. By using an RA-inducible reporter, it is found that the wild type CRABP-I exerts biphasic effects on RA induction of the reporter. The early (at 12 h) effect is to enhance RA induction, whereas the delayed (at 24 h) effect is to suppress RA induction. In consistence with their RA binding property, the R 131A mutant loses both its early and delayed biological activities, whereas the Y133F mutant remains as effective as the wild type. It is concluded that CRABP-I over-expression exerts biphasic effects on RA-mediated gene expression, and that Arg131, but not Tyr 133, is essential for a high RA-binding affinity of this protein as well as its biological activity.
    Materialart: Digitale Medien
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  • 6
    ISSN: 1058-8388
    Schlagwort(e): CRABP-I ; P19 cells ; DNA methylation ; Gene expression ; Life and Medical Sciences ; Cell & Developmental Biology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Medizin
    Notizen: The mouse cellular retinoic acid binding protein-I (CRABP-I) gene is specifically up-regulated by retinoic acid (RA) in P19 mouse embryonal carcinoma cells, and its expression in animals is spatially and temporally restricted to RA-sensitive tissues during embryonic development. This study demonstrates that, in adult mouse tissues and P19 cells where the expression of CRABP-I is detected at the basal level, the 5′- flanking region of the CRABP-I gene is hypermethylated at the C residues of all the Hpa II sites. Conversely, in mouse embryos during early stages of development when the expression of CRABP-I gene is detected at a much higher level, this region is demethylated at these Hpa II sites. In P19, enhancement on the RA-induced up-regulation of CRABP-I can be observed in cells treated with 5-azacytidine (5-AzaC) in conjunction with RA, where partial demethylation in the 5′-flanking region of CRABP-I gene is observed. Nuclear run-on experiments indicate that increased message levels of CRABP-I in P19 cells can be accounted for, at least partially, by increases in its transcription rates. The induction of retinoic acid receptor (RAR) β by RA can also be enhanced by 5-AzaC, but to a much lesser degree. In contrast, all the Hpa II sites in the structural gene portion, at least in the first two exons, are fully demethylated at the C residues. © 1994 Wiley-Liss, Inc.
    Zusätzliches Material: 9 Ill.
    Materialart: Digitale Medien
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