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81.
[Co(P1)], which was designed on the basis of potential hydrogen-bonding interactions in the metal-nitrene intermediate, is a highly active aziridination catalyst with azides. [Co(P1)] can effectively aziridinate various aromatic olefins with arylsulfonyl azides under mild conditions, forming sulfonylated aziridines in excellent yields. The Co-based system enjoys several attributes associated with the relatively low cost of cobalt and the wide accessibility of arylsulfonyl azides. Furthermore, it generates stable dinitrogen as the only byproduct. 相似文献
82.
83.
Michael A. Morris Alexander Vallmitjana Fabian Grein Tanja Schneider Melina Arts Chelsea R. Jones Betty T. Nguyen Mohammad H. Hashemian Melody Malek Enrico Gratton James S. Nowick 《Chemical science》2022,13(26):7747
Teixobactin has been the source of intensive study and interest as a promising antibiotic, because of its excellent activity against drug-resistant Gram-positive pathogens and its novel but not yet fully understood mechanism of action that precludes drug resistance. Recent studies have demonstrated that the mode of action of teixobactin is more complicated than initially thought, with supramolecular assembly of the antibiotic appearing to play a critical role in the binding process. Further studies of the interactions of teixobactin with bacteria and its molecular targets offer the promise of providing deeper insights into its novel mechanism of action and guiding the design of additional drug candidates and analogues. The current study reports the preparation and study of teixobactin analogues bearing a variety of fluorophores. Structured illumination microscopy of the fluorescent teixobactin analogues with B. subtilis enables super-resolution visualization of the interaction of teixobactin with bacterial cell walls and permits the observation of aggregated clusters of the antibiotic on the bacteria. Förster resonance energy transfer (FRET) microscopy further elucidates the supramolecular assembly by showing that fluorescent teixobactin molecules co-localize within a few nanometers on B. subtilis. Fluorescence microscopy over time with a fluorescent teixobactin analogue and propidium iodide in B. subtilis reveals a correlation between cell death and binding of the antibiotic to cellular targets, followed by lysis of cells. Collectively, these studies provide new insights into the binding of teixobactin to Gram-positive bacteria, its supramolecular mechanism of action, and the lysis of bacteria that follows.FRET microscopy experiments demonstrate supramolecular assembly of teixobactin molecules on Bacillus subtilis, providing further evidence that teixobactin is a supramolecular antibiotic. 相似文献
84.
H. Werner L. W. Winkler Th. von Fellenberg H. J. Almquist J. V. Givens E. Iselin Ivar Bang und Georges Deniges 《Fresenius' Journal of Analytical Chemistry》1935,100(3-4):140-141
Ohne Zusammenfassung 相似文献
85.
Mathew Kattathu Joseph Ottenfeld Chelsea Levesque Steven Keller Russ 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(2):1005-1017
Journal of Radioanalytical and Nuclear Chemistry - Through high fidelity measurements of four different plutonium certified reference material standards from New Brunswick Laboratory, the mass... 相似文献
86.
Ryan D. Cohen Josep Saurí Chelsea A. Huff Shane W. Krska Gary E. Martin 《Magnetic resonance in chemistry : MRC》2016,54(11):897-900
1,1‐ADEQUATE is a powerful and robust NMR experiment to establish carbon–carbon connectivities using modest sample quantities when cryogenic probe technology is available. Yet potential pitfalls of applying this method are not widely appreciated, such as weak or missing 1JCC correlations in strongly coupled 13C‐13C AB spin systems and unusually large multi‐bond (nJCC) correlations associated with particular functional groups. These large nJCC correlations observed in 1,1‐ADEQUATE spectra could be mistaken for 1JCC correlations. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
87.
Jeffrey W. Guthrie Robert T. LimmerEric A. Brooks Chelsea C. WisnewskiNnekia D. Loggins-Davis Abderraouf Bouzid 《Analytica chimica acta》2015
An immunoassay based on CE–LIF was developed for the simultaneous detection of cyclobutane pyrimidine dimers (CPDs) and pyrimidine 6-4 pyrimidone photoproducts (6-4PPs) in genomic DNA irradiated with UVB or natural sunlight. Human cells were first exposed to varying amounts of UVB or natural sunlight to induce DNA damage. Genomic DNA was extracted and incubated with anti-CPD and anti-6-4PP primary antibodies attached to secondary antibodies with a fluorescent quantum dot (QD) reporter that emitted either red or yellow fluorescence. CE was used to separate the unbound antibodies from those bound to the photoproducts, and LIF with appropriate optical filters was used to separate the fluorescence signals from each QD to individual photomultiplier tubes for simultaneous photoproduct detection. Using this strategy, photoproducts were detected from ∼6 ng (200 ng μL−1) of DNA under a low UVB fluence of 65 J m−2 for CPDs or 195 J m−2 for 6-4PPs. This assay was also the first to demonstrate the detection of CPDs in human cells after only 15 min of irradiation under natural sunlight. 相似文献
88.
Eric Jacobsen Mihir K. Chavda Kokou M. Zikpi Stephanie L. Waggoner Daniel J. Passini Jesse A. Wolfe Robert Larson Chelsea Beckley Christopher G. Hamaker Shawn R. Hitchcock 《Tetrahedron letters》2017,58(31):3073-3077
A reagent combination of toluenesulfinic acid and trimethylacetyl chloride affords a putative trimethylacetic p-toluenesulfinic anhydride. This reagent has been used to prepare a series of sulfinate esters from primary and secondary alcohols. In addition, the reagent was used to convert Baylis-Hillman substrates into allylic sulfones. Attempts to use the reagent to convert amines to sulfinamides were unsuccessful. In contrast, the use of 2-pyrrolidinone afforded N-p-toluenesulfinyl pyrrolidinone in 64% yield. The use of a chiral 4-benzyl-1,3-oxazolidinone or 4-benzyl-1,3-oxazolidine-2-thione led to the isolation of S-p-tolyl p-toluenethiosulfonate. 相似文献
89.
A reproducible analytical method for determination of nitrocellulose in soil is described. The new method provides the precision and accuracy needed for quantitation of nitrocellulose in soils to enable worker safety on contaminated sites. The method utilizes water and ethanol washes to remove co-contaminants, acetone extraction of nitrocellulose, and base hydrolysis of the extract to reduce nitrate groups. The hydrolysate is then neutralized and analyzed by ion chromatography for determination of free nitrate and nitrite. A variety of bases for hydrolysis and acids for neutralization were evaluated, with 5N sodium hydroxide and carbon dioxide giving the most complete hydrolysis and interference-free neutralization, respectively. The concentration of nitrocellulose in the soil is calculated from the concentrations of nitrate and nitrite and the weight percentage of nitrogen content in nitrocellulose. The laboratory detection limit for the analysis is 10mg/kg. The method acceptance range for recovery of nitrocellulose from control samples is 78-105%. 相似文献
90.