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391.
Paul Andrewes William R. Cullen Jrg Feldmann Iris Koch Elena Polishchuk Kenneth J. Reimer 《应用有机金属化学》1998,12(12):827-842
Cultures of the fungus Scopulariopsis brevicaulis were grown in antimony-rich media. Although volatile compounds of other elements were readily detected in the culture headspace, volatile antimony compounds were formed irreproducibly and at only ultratrace levels. In order to monitor the media for nonvolatile methylantimony compounds, a method of sample preparation was developed, based on solid-phase extraction. This enabled the separation of large quantities of soluble inorganic antimony species from trace amounts of organoantimony compounds before speciation by HG–GC–AAS. By this methodology methylated antimony compounds were detected at concentrations of 0.8– 7.1 µg Sbl−1 in all media in which S. brevicaulis was grown in the presence of antimony(III) compounds. These methylantimony species were not detected in any of the nonliving or medium-only controls. Methylated compounds were not detected where S. brevicaulis was grown in the presence of antimony(V) compounds. This is the first study to show that antimony(III) compounds are biomethylated by S. brevicaulis under aerobic-only growth conditions. Copyright © 1998 John Wiley & Sons, Ltd. 相似文献
392.
A simple, rapid, and sensitive HPLC method based on 9H‐fluoren‐9‐ylmethyl chloroformate derivatization for the quantification of sertraline in rat plasma has been developed, requiring a plasma sample of only 0.1 mL, which was deproteinized and derivatized for 5 min in two single steps. The obtained derivative was stable at room temperature and was determined by HPLC using a fluorescence detector. The analytical column was a C(18) column and the mobile phase was acetonitrile and water (80:20, v/v). Calibration curves were linear in the range of 10–500 ng/mL. The limit of detection was approximately 3 ng/mL, and the lower limit of quantification was established at 10 ng/mL. The bias of the method was lower than 10%, and the within day as well as between day, relative standard deviations were lower than 12%. This analytical method was successfully applied to characterize sertraline pharmacokinetics in rats following intravenous (t1/2 = 213 ± 48 min, Cl = 43.1 ± 8.7 mL/min, Vd = 11560 ± 1861 mL) and oral (Cmax = 156 ± 76 ng/mL, tmax = 63.8 ± 16.3 min) administration of 2 and 5 mg, respectively. 相似文献
393.
CrO(3) oxidation experiments conducted on atropisomeric forms of 2 (2(paco), 2(1,3)(-)(alt), and 2(1,2)(-)(alt)) indicate that under the reaction conditions only methylene groups located between pairs of geminal rings oriented in an anti disposition are oxidized to carbonyls. NMR data suggest that the tetrahydroxydioxocalix[4]arenes 7 and 9 adopt the partial cone and 1,2-alternate conformations, respectively. In the crystal structure of 7.2EtOAc the dioxocalixarene adopts a partial cone conformation, whereas 9 adopts in the crystal a 1,2-alternate conformation. In both conformations, pairs of geminal rings connected to a carbonyl are oriented in an anti fashion. The relative stability of the partial cone and 1,2-alternate conformations of 7 and 9 is underestimated by MM3 calculations. The topomerization barriers of 7 and 9 are 12.8 and 13.6 kcal mol(-)(1), respectively. 相似文献
394.
A new synthesis of (?)‐(R)‐muscone ((R)‐ 1 ) by means of enantioselective protonation of a bicyclic ketone enolate as the key step (see 6 →(S)‐ 4 in Scheme 2) is presented. The C15 macrocyclic system is obtained by ozonolysis (Scheme 7). 相似文献
395.
Edna Bode Antje K. Heinrich Merle Hirschmann Desalegne Abebew Yan‐Ni Shi Tien Duy Vo Frank Wesche Yi‐Ming Shi Peter Grün Svenja Simonyi Nadine Keller Yvonne Engel Sebastian Wenski Reuel Bennet Sophie Beyer Iris Bischoff Anthony Buaya Sophie Brandt Ibrahim Cakmak Harun imen Simone Eckstein Denia Frank Robert Fürst Martin Gand Gerd Geisslinger Selcuk Hazir Marina Henke Ralf Heermann Virginie Lecaudey Wilhelm Schfer Susanne Schiffmann Anja Schüffler Rebecca Schwenk Marisa Skaljac Eckhard Thines Marco Thines Thomas Ulshfer Andreas Vilcinskas Thomas A. Wichelhaus Helge B. Bode 《Angewandte Chemie (International ed. in English)》2019,58(52):19114-19114
396.
Jens Pettelkau Iris Thondorf Stephan Theisgen Hauke Lilie Thomas Schröder Christian Arlt Christian H. Ihling Andrea Sinz 《Journal of the American Society for Mass Spectrometry》2013,24(12):1969-1979
The topology of the GCAP-2 homodimer was investigated by chemical cross-linking and high resolution mass spectrometry. Complementary conducted size-exclusion chromatography and analytical ultracentrifugation studies indicated that GCAP-2 forms a homodimer both in the absence and in the presence of Ca2+. In-depth MS and MS/MS analysis of the cross-linked products was aided by 15 ? N-labeled GCAP-2. The use of isotope-labeled protein delivered reliable structural information on the GCAP-2 homodimer, enabling an unambiguous discrimination between cross-links within one monomer (intramolecular) or between two subunits (intermolecular). The limited number of cross-links obtained in the Ca2+-bound state allowed us to deduce a defined homodimeric GCAP-2 structure by a docking and molecular dynamics approach. In the Ca2+-free state, GCAP-2 is more flexible as indicated by the higher number of cross-links. We consider stable isotope-labeling to be indispensable for deriving reliable structural information from chemical cross-linking data of multi-subunit protein assemblies. Figure
? 相似文献
397.
Luís A. S. A. De Prado Iris L. Torriani Inez V. P. Yoshida 《Journal of polymer science. Part A, Polymer chemistry》2010,48(5):1220-1229
Self‐supported translucent films constituted of poly(n‐octylsilsesquioxane) or poly(n‐dodecylsilsesquioxane) were obtained from the hydrolysis and condensation of n‐octyltriethoxysilane (OTES) or n‐dodecyltriethoxysilane (DTES), respectively. Dense films were obtained in the absence of organic solvents, with dibutyltin diacetate as catalyst. These films exhibited good optical transparency and thermal stability. The incorporation of oligomeric dimethylsiloxane units (DMe,Me) in these materials, derived from silanol‐terminated poly(dimethylsiloxane) (PDMS) or 1,1,3,3‐tetramethyl‐1,3‐diethoxydisiloxane (TMDES), was carried out during the hydrolysis and condensation of OTES and DTES and was confirmed by solid‐state 29Si NMR. Poly(n‐octylsilsesquioxane) showed a glass‐transition temperature at ?65 °C, due to the increase in the free volume, promoted by the bulky n‐octyl groups. The differential scanning calorimetric (DSC) curves of the polymer derived from DTES were characterized by first‐order transitions at temperatures ranging from ?15.8 to ?0.7 °C. Further studies of these networks by low‐temperature XRD evidenced narrowing of the diffraction halos suggesting a partial order–disorder transition for these materials at lower temperatures. Good thermal stability up to 350 °C and the solvent‐free production process make these polymers potential candidates for the development of self‐supported hydrophobic protective coatings. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1220–1229, 2010 相似文献
398.
Parameterization of the Hamiltonian Dielectric Solvent (HADES) Reaction‐Field Method for the Solvation Free Energies of Amino Acid Side‐Chain Analogs 下载免费PDF全文
Optimization of the Hamiltonian dielectric solvent (HADES) method for biomolecular simulations in a dielectric continuum is presented with the goal of calculating accurate absolute solvation free energies while retaining the model’s accuracy in predicting conformational free‐energy differences. The solvation free energies of neutral and polar amino acid side‐chain analogs calculated by using HADES, which may optionally include nonpolar contributions, were optimized against experimental data to reach a chemical accuracy of about 0.5 kcal mol?1. The new parameters were evaluated for charged side‐chain analogs. The HADES results were compared with explicit‐solvent, generalized Born, Poisson–Boltzmann, and QM‐based methods. The potentials of mean force (PMFs) between pairs of side‐chain analogs obtained by using HADES and explicit‐solvent simulations were used to evaluate the effects of the improved parameters optimized for solvation free energies on intermolecular potentials. 相似文献
399.
400.
Natural‐Product‐Inspired Aminoepoxybenzoquinones Kill Members of the Gram‐Negative Pathogen Salmonella by Attenuating Cellular Stress Response 下载免费PDF全文
Dr. Franziska A. Mandl Volker C. Kirsch Dr. Ilke Ugur Elena Kunold Jan Vomacka Christian Fetzer Dr. Sabine Schneider Dr. Klaus Richter Prof. Dr. Thilo M. Fuchs Prof. Dr. Iris Antes Prof. Dr. Stephan A. Sieber 《Angewandte Chemie (International ed. in English)》2016,55(47):14852-14857
Gram‐negative bacteria represent a challenging task for antibacterial drug discovery owing to their impermeable cell membrane and restricted uptake of small molecules. We herein describe the synthesis of natural‐product‐derived epoxycyclohexenones and explore their antibiotic activity against several pathogenic bacteria. A compound with activity against Salmonella Typhimurium was identified, and the target enzymes were unraveled by quantitative chemical proteomics. Importantly, two protein hits were linked to bacterial stress response, and corresponding assays revealed an elevated susceptibility to reactive oxygen species upon compound treatment. The consolidated inhibition of these targets provides a rationale for antibacterial activity and highlights epoxycyclohexenones as natural product scaffolds with suitable properties for killing Gram‐negative Salmonella. 相似文献