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291.
Anthony M. Haag Audrie M. Medina Ariel E. Royall Norbert K. Herzog David W. Niesel 《Journal of mass spectrometry : JMS》2013,48(6):732-739
Antibiotic resistance is a growing problem worldwide. For this reason, clinical laboratories often determine the susceptibility of the bacterial isolate to a number of different antibiotics in order to establish the most effective antibiotic for treatment. Unfortunately, current susceptibility assays are time consuming. Antibiotic resistance often involves the chemical modification of an antibiotic to an inactive form by an enzyme expressed by the bacterium. Selected reaction monitoring (SRM) has the ability to quickly monitor and identify these chemical changes in an unprecedented time scale. In this work, we used SRM as a technique to determine the susceptibility of several different antibiotics to the chemically modifying enzymes β‐lactamase and chloramphenicol acetyltransferase, enzymes used by bacteria to confer resistance to major classes of commonly used antibiotics. We also used this technique to directly monitor the effects of resistant bacteria grown in a broth containing a specific antibiotic. Because SRM is highly selective and can also identify chemical changes in a multitude of antibiotics in a single assay, SRM has the ability to detect organisms that are resistant to multiple antibiotics in a single assay. For these reasons, the use of SRM greatly reduces the time it takes to determine the susceptibility or resistance of an organism to a multitude of antibiotics by eliminating the time‐consuming process found in other currently used methods. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
292.
Photoresponsive Switches at Surfaces Based on Supramolecular Functionalization with Azobenzene–Oligoglycerol Conjugates 下载免费PDF全文
Olaf Nachtigall Dr. Christian Kördel Leonhard H. Urner Prof. Dr. Rainer Haag 《Angewandte Chemie (International ed. in English)》2014,53(36):9669-9673
The synthesis, supramolecular complexation, and switching of new bifunctional azobenzene–oligoglycerol conjugates in different environments is reported. Through the formation of host–guest complexes with surface immobilized β‐cyclodextrin receptors, the bifunctional switches were coupled to gold surfaces. The isomerization of the amphiphilic azobenzene derivatives was examined in solution, on gold nanoparticles, and on planar gold surfaces. The wettability of functionalized gold surfaces can be reversibly switched under light‐illumination with two different wavelengths. Besides the photoisomerization processes and concomitant effects on functionality, the thermal cis to trans isomerization of the conjugates and their complexes was monitored. Thermal half‐lives of the cis isomers were calculated for different environments. Surprisingly, the half‐lives on gold nanoparticles were significantly smaller compared to planar gold surfaces. 相似文献
293.
Ria Thielhorn Isabelle Heing-Becker Nadja Hümpfer Jakob Rentsch Rainer Haag Kai Licha Helge Ewers 《Angewandte Chemie (International ed. in English)》2023,62(28):e202302318
Expansion microscopy (ExM) is a recently developed technique that allows for the resolution of structures below the diffraction limit by physically enlarging a hydrogel-embedded facsimile of the biological sample. The target structure is labeled and this label must be retained in a relative position true to the original, smaller state before expansion by linking it into the gel. However, gel formation and digestion lead to a significant loss in target-delivered label, resulting in weak signal. To overcome this problem, we have here developed an agent combining targeting, fluorescent labeling and gel linkage in a single small molecule. Similar approaches in the past have still suffered from significant loss of label. Here we show that this loss is due to insufficient surface grafting of fluorophores into the hydrogel and develop a solution by increasing the amount of target-bound monomers. Overall, we obtain a significant improvement in fluorescence signal retention and our new dye allows the resolution of nuclear pores as ring-like structures, similar to STED microscopy. We furthermore provide mechanistic insight into dye retention in ExM. 相似文献
294.
Isozeaxanthin: Chirality and Enantioselective Synthesis of (4R,4′R)-Isozeaxanthin ((?)-(4R,4′R)-β, β-Carotin-4,4′-diol) The absolute configuration of optically active isozeaxanthin was established by synthesis using (?)-(R)-4-hydroxy-β-ionon ( 2 ) [18] as starting material. 相似文献
295.
Nico Scharnagl Andreas Lendlein Rainer Haag Georg Oenbrink 《Nachrichten aus der Chemie》2010,58(12):1307-1308
296.
Govindarao Sathyamoorthi Lionel T. Wolford Anthony M. Haag Joseph H. Boyer 《Heteroatom Chemistry》1994,5(3):245-249
Treatment with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) oxidized 2,6-diethyl-1,3,5,7,8-pentamethylpyrromethene–BF2 complex 1 , 13,14-trimethyl-2, 3, 4, 5,9,10,11,12-octahydroindomethene–BF2 complex 5 , and 1,3,5,7,8-pentamethyl-1,2,3,5,6,7-hexahydropyromethene–BF2 complex 8 to the weakly fluorescent 3-formyl, 5-oxo, and 8-formyl derivatives 4 , 6 , and 9 , respectively. The dye 1 was oxidized by lead tetraacetate to 1,7,8-trimethyl-2,6-diethyl-3,5-diacetoxymethylpyrromethene–BF2 complex 12 [λf (ethanol) 538 nm, Φ 0.62, λlas (ethanol) 555–570 nm]. Catalytic reduction (Pd/C) converted the aldehyde 4 to 2,6-diethyl-3-hydroxymethyl-1,5,7,8-tetramethylpyrromethene–BF2 complex 10 [λf (ethanol) 537 nm, Φ 0.70, λlas (ethanol) 547–575 nm]. 相似文献