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91.
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Leeuwenburgh MA Geurink PP Klein T Kauffman HF van der Marel GA Bischoff R Overkleeft HS 《Organic letters》2006,8(8):1705-1708
[reaction: see text] A novel solid-phase synthesis strategy toward succinylhydroxamate peptides, using an appropriately protected hydroxamate building block, is described. Rapid and efficient access is gained to amine-functionalized peptides, which can be decorated with, for instance, a fluorescent label. In addition, we demonstrate an on-resin synthesis of a biotinylated photoactivatable hydroxamate peptide, which can be used as an activity-based probe for matrix metalloproteinases and ADAMs. 相似文献
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Anne P. Vonderheide Kurt Thaxton Peter E. Kauffman Jeffrey N. Morgan 《Microchemical Journal》2010,95(2):279-284
Polybrominated diphenyl ethers (PBDEs) fall into the class of compounds known as brominated flame retardants and their incorporation in a multitude of products is responsible for saving numerous lives. However, toxicology studies have alerted researchers to the potential adverse health effects that may develop as a result of prolonged or extreme exposure to these compounds. Frequent disposal and subsequent leaching has focused concern on environmental concentrations and current reports cite increasing levels. Method development continues in support of this research and the present work examines the feasibility of utilizing gas chromatography ion trap mass spectrometry operating in positive ion chemical ionization mode. In the evaluation of reagents for chemical ionization (methane, methanol and acetonitrile), comparative results of all three reagents demonstrated more difficult protonation as the number of bromine atoms increased. Methane, possessing the lowest proton affinity, provided the highest response for the analytes. Further, when methane chemical ionization was compared to electron impact ionization, the tetra-congener showed approximately 8× greater sensitivity and the penta- and hexa-congeners demonstrated approximately 2× greater. CI parameters, such as ionization and reaction times, were optimized to provide the highest analyte response and this was followed by the investigation of the employment of MSn. In the this mode, optimal excitation amplitude delivered sufficient fragmentation while maintaining maximum signal, yielding final instrument detection limits in the sub µg L− 1 range. 相似文献
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Joel M. Kauffman Peter T. Litak Walter J. Boyko 《Journal of heterocyclic chemistry》1995,32(5):1541-1555
Dibenzofurans, a dibenzothiophene, and carbazoles, each substituted with a 2-benzoxazolyl group as well as an ortho-hydroxyl group, were synthesized to produce fluors with fluorescence due to excited-state intramolecular proton-transfer. The orientations for Friedel-Crafts acylation of 3-methoxydibenzothio-phene and of the analogous carbazole were determined. The fluors displayed absorption peaks in the 330–385 nm region with molar extinction coefficients up to 57,000. Fluorescence quantum efficiencies of 0.17–0.44 were obtained at wavelengths that had peak values from 540–600 nm. The fluors are of potential use as wavelength shifters in scintillating polystyrene fibers. 相似文献
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