37 research outputs found
Determination of selenium in biological materials by stable isotope dilution gas chromatography-mass spectrometry
Évolution de la Composition Gazeuse de L'Air Expiré, Chez L'Homme, Au Cours des Ventilations Calme et Forcée
Determination of Selenium in Biological Materials by Stable Isotope Dilution Gas Chromatography-Mass Spectrometry
Selenium can be determined quantitatively in biological samples after digestion using nitric acid, orthophosphoric acid, and hydrogen peroxide and the formation of 5-nitropiazselenol. Samples are spiked with enriched 82Se and lsotoplc ratio of 80Se to 82Se is measured by combined gas chromatographymass spectrometry using dual ion monitoring. Precise determination at the parts-per-billion level is possible. The accuracy of the method Is verlfied by using standard reference materials
Comparison of the performance of the single- and triple-slot air-acetylene burners for atomic absorption spectrometry
Behavior of metal particles compared to organometallic compounds measured by flame atomic absorption spectrophotometry
Use of the nitrous oxide-aceytlene flame for determination of arsenic and selenium by atomic absorption spectrometry
In Vitro and In Vivo Activities of Novel, Semisynthetic Thiopeptide Inhibitors of Bacterial Elongation Factor Tu â–¿
Recently, we identified aminothiazole derivatives of GE2270 A. These novel semisynthetic congeners, like GE2270 A, target the essential bacterial protein elongation factor Tu (EF-Tu). Medicinal chemistry optimization of lead molecules led to the identification of preclinical development candidates 1 and 2. These cycloalklycarboxylic acid derivatives show activity against difficult to treat Gram-positive pathogens and demonstrate increased aqueous solubility compared to GE2270 A. We describe here the in vitro and in vivo activities of compounds 1 and 2 compared to marketed antibiotics. Compounds 1 and 2 were potent against clinical isolates of methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococci (MIC90 ≤ 0.25 μg/ml) but weaker against the streptococci (MIC90 ≥ 4 μg/ml). Like GE2270 A, the derivatives inhibited bacterial protein synthesis and selected for spontaneous loss of susceptibility via mutations in the tuf gene, encoding EF-Tu. The mutants were not cross-resistant to other antibiotic classes. In a mouse systemic infection model, compounds 1 and 2 protected mice from lethal S. aureus infections with 50% effective doses (ED50) of 5.2 and 4.3 mg/kg, respectively. Similarly, compounds 1 and 2 protected mice from lethal systemic E. faecalis infections with ED50 of 0.56 and 0.23 mg/kg, respectively. In summary, compounds 1 and 2 are active in vitro and in vivo activity against difficult-to-treat Gram-positive bacterial infections and represent a promising new class of antibacterials for use in human therapy