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41.
An enantioselective HPLC bioassay has been developed relying on extraction of (R)- and (S)-atenolol from alkalinized plasma or serum (pH > 12) into dichloromethane containing 5% (v/v) 1-butanol followed by an achiral derivatization of the drug with phosgene leading to (R)- and (S)-oxazolidine-2-one derivatives. Under these conditions there was quantitative conversion of the acetamido group to the corresponding nitrile. These stable derivatives were separated on a (R,R)-diaminocylohexane-dinitrobenzoyl chiral stationary phase [(R,R)-DACH-DNB] using dichloromethane/methanol 98/2 as mobile phase. Determination limits of 0.5 ng for (R)- and 0.6 ng for (S)-atenolol could be achieved using fluorimetric detection. The assay was applied to a human pharmacokinetic study which was performed in a randomized cross-over, double-blind fashion in 12 healthy volunteers, administering single oral doses of 100 mg (R,S)-, 50 mg (R)-, and 50 mg (S)-atenolol AUC0–24 and Cmax values of (R)-atenolol were slightly but significant higher than those of (S)-atenolol. The R/S ratios were 1.09 for AUC(R)/AUC(S) and 1.03 for Cmax (R)/Cmax(S) (P < 0.01) respectively after administration of the racemic drug. However, there were no differences between AUC, Cmax, and t½ values of each enantiomer, whether they were administered as single enantiometers or in the form of its racemic mixture. © 1993 Wiley-Liss, Inc. 相似文献
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Marc Mathieu Christian Lehmann Alain Razaname Gabriele Tuchscherer 《Letters in Peptide Science》1997,4(2):95-100
The assembly of helical and -sheet peptide blocks containing reactive chain ends results inhighly branched chain architectures (locked-in folds) mimicking native tertiary structures.This molecular kit strategy allows to bypass the protein folding problem in protein de novodesign and gives access to protein mimetics of high thermodynamic stability. The validity ofthis concept is exemplified for the design and synthesis of locked-in folds mimicking the zincfinger and MHC folding motifs. 相似文献
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Molecular cloning of a new receptor-like kinase gene encoded at the Lr10 disease resistance locus of wheat 总被引:32,自引:0,他引:32
Catherine Feuillet Gabriele Schachermayr Beat Keller 《The Plant journal : for cell and molecular biology》1997,11(1):45-52
More than 100 resistance genes against wheat rust pathogens have been described in wheat and its relatives. Although many of them have been extensively used in wheat resistance breeding, none of these resistance loci has yet been analyzed at the molecular level. By screening a set of near-isogenic lines carrying different leaf rust resistance genes with a wheat probe encoding a serine/threonine protein kinase, we detected a polymorphic DNA fragment in the line with the Lr10 resistance gene. This fragment mapped to the Lr10 disease resistance locus and encodes a receptor-like protein kinase which we called LRK10. LRK10 contains a new type of extracellular domain not found in known plant or animal receptor kinases. Several conserved amino acids in S-domain glycoproteins and receptor-like kinases were also found in LRK10, suggesting that LRK10 and S-domain proteins belong to the same superfamily of specific recognition molecules in plants. Lrk10 was expressed at low levels in young seedlings and belongs to a gene family. Analysis of wheat lines with and without the Lr10 gene demonstrated that Lrk10 and Lr10 belong to the same genetic locus. We conclude that gene isolation based on protein kinase homology can identify new receptor domains and provide candidates for disease resistance genes in the complex wheat genome. 相似文献
46.
tRNA genes and pathogenicity islands: influence on virulence and metabolic properties of uropathogenic Escherichia coli 总被引:13,自引:2,他引:11
47.
André W. Schram Marianne Dreissen Johan Bastiaannet Wilma E. Donker-Koopman Elisabeth M. Brouwer-Kelder Gabriele Weitz John A. Barranger Konrad Sandhoff Joseph M. Tager 《Bioscience reports》1984,4(12):1051-1057
The immunoblotting technique was used to identify sphingomyeJinase protein in samples of tissue and urine after subjection to poIyacrylamide-gel etectrophoresis in the presence of sodium dodecyl sulphate. In a sphingomyelinase preparation purified from control urine a prominent band was seen with an Mr of 28 000 Da. Glycoprotein fractions from urine and placenta, a membrane extract from spleen, and a partially purified sphingomyelinase preparation from placenta contained the 28 000-Da band plus additional, higher-Mr bands. The 28 000-Da band was detectable in urine from a patient with Niemann-Pick disease type C, but not in urine from patients with Niemann-Pick disease types A and B. It is concluded t h a t sphingomyeJinase is composed of at least one polypeptide with an Mr of 28 000 Da and that this polypeptide is deficient in the urine of patients with Niemann-Pick disease types A and B. 相似文献
48.
The dependence of growth on nickel supply was studied in Chlorella emersonii 211-8b. After transfer to Ni2+ deficient medium containing only 0.5±0.2 g/l of Ni2+, production of biomass or daughter cells dropped to 55±5% of the controls, and the cells became chlorotic. These symptoms of deficiency disappeared completely by supplying adequate amounts of nickel. They were, however, only partially reversible by cobalt. It is concluded that nickel is an essential micronutrient for C. emersonii, although this organism lacks the nickel enzyme, urease.Gratefully dedicated to Prof. Hans Adolf von Stosch on the occasion of his 70th birthday 相似文献
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We report that two species of basidiomycete fungi (Polyporus versicolor and Poria monticola) grow in minimal liquid or solid medium when supplemented with crushed lignite coal. The fungi also grow directly on crushed lignite coal. The growth of both fungi was observed qualitatively as the production and extension of hyphae. No fungal growth occurred in minimal agar medium without coal. The fungi degraded solid lignite coal to a black liquid product which never appeared in cultures unless fungi and coal were present together. Apparently, lignite coal can serve as the principal substrate for the growth of the fungi. Infrared analyses of the liquid products of lignite degradation showed both similarities to and differences from the original lignite. 相似文献