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901.
A fluorimetric assay for cortisol 总被引:2,自引:0,他引:2
Appel D Schmid RD Dragan CA Bureik M Urlacher VB 《Analytical and bioanalytical chemistry》2005,383(2):182-186
A simple, rapid and sensitive fluorimetric assay for the quantitative determination of cortisol is reported. The assay is
based on the formation of a fluorescent dye when cortisol is incubated with a mixture of sulfuric acid and acetic acid. The
fluorescence spectrum recorded for the resulting dye shows a maximum extinction at 475 nm and a maximum emission at 525 nm.
The solvent 2-methyl-4-pentanone was used for extraction and was found to act as a fluorescence amplifier. A limit of detection
of 2.7 μM was achieved, making it possible to forego solvent evaporation. The assay suffers minor interference from 11-deoxycortisol
which exhibits low fluorescence at λ
ex: 460 nm; λ
em: 505 nm. Typical standard deviations were below 4%. We validated the assay using a biotransformation with recombinant Schizosaccharomyces pombe which regioselectively hydroxylates 11-deoxycortisol to cortisol. The method described herein is suitable for preliminary
screening of microorganisms capable of steroid hydroxylation. 相似文献
902.
Davor Margeti? 《Tetrahedron》2007,63(20):4338-4346
Four new substituted methano-bridged or heteroatom-bridged norbornadienomaleic anhydrides have been prepared and converted to sesquinorbornadiene anhydrides by reaction with cyclic 1,3-dienes. The versatility of parity reversal, in conjunction with N-substituent steric effects, has been used to produce all three possible stereoisomers of the N,O-sesquinorbornadiene anhydrides in separate, stereoselective cycloadditions. The anhydrides have been synthesized by cyclization of their diacids (in situ production) or by flash vacuum pyrolysis of their furan adducts (yielding crystalline products); further fragmentation occurs at these or higher temperatures to produce five-membered carbocyclic or heterocyclic anhydrides. Activation energies have been evaluated for the fragmentation and cycloaddition processes using DFT calculations (B3LYP/6-31G∗) and these calculations correctly predict, which reaction can be intercepted at the norbornadienomaleic anhydride stage and preferred stereochemistry of cycloadducts. 相似文献
903.
Cheng-Zhu Wu Xing Fu Cai Seong Su Hong Eun-Kyoung Seo Ji-Xing Nan Jung Joon Lee 《Tetrahedron letters》2007,48(50):8861-8864
Two novel dimeric meroterpenoids, bisbakuchiols A and B, along with (S)-bakuchiol were isolated from the seeds of Psoralea corylifolia L. (Fabaceae). Bisbakuchiols A and B contain an unprecedented dimeric meroterpenoid skeleton in which two meroterpenes are linked through a dioxane bridge. All compounds were evaluated for their potential to inhibit hypoxia-inducible factor-1 (HIF-1) activation induced by hypoxia in a HIF-1-mediated reporter gene assay in AGS human gastric cancer cells. (S)-Bakuchiol inhibited hypoxic activation of HIF-1 with an IC50 value of 6.1 μM. 相似文献
904.
This report describes a new type of intra-intermolecular criss-cross cycloadditions. Thermal reactions of unsymmetrical allenylazines in the presence of alkynes led to three fused five-membered heterocycles in some cases. In the case of unsymmetrical substituted alkynes, a regioselectivity was observed. The molecular structures of all products are discussed. One X-ray crystal structure is also reported. 相似文献
905.
906.
先将3-蒈烯分子中的碳碳双键氧化开环制得蒈酮酸,再将羰基还原成亚甲基得到蒈酸,酰氯化后与系列酰肼发生N-酰化反应合成了14个新型蒈酸基双酰肼化合物(5a~5n),其结构经UV-Vis、1H NMR、13C NMR、 FT-IR和MS(ESI)表征,并测试了目标化合物的抑菌和除草活性。结果显示:在用药量为50 μg·mL-1时,目标化合物对花生褐斑病菌、小麦赤霉病菌、黄瓜枯萎病菌、苹果轮纹病菌、番茄早疫病菌、玉米小斑病菌、西瓜炭疽病菌以及水稻纹枯病菌等8种植物病原菌具有一定的抑制活性,其中化合物蒈酸基α-噻吩甲酰肼5f(R=α-thiophene)对苹果轮纹病菌的抑制率达85.0%,优于阳性对照百菌清。在用药量为100 μg·mL-1时,化合物蒈酸基3′,4′-二甲氧基苯甲酰肼5j(R=3′,4′-OMe-Ph)、蒈酸基-m-甲氧基苯甲酰肼5d(R=m-OMe-Ph)、蒈酸基-m-甲基苯甲酰肼5b(R=m-Me-Ph)和蒈酸基苯甲酰肼5a(R=Ph)对油菜胚根生长的抑制率分别为88.5%、 86.1%、 85.1%和82.6%(均为A级活性水平),优于阳性对照丙炔氟草胺。 相似文献
907.
Hexenes give large amounts of hexane and isomeric hexenes over EUROPT-1. A constant hydrocarbon coverage can be assumed in the steady-state period of the reaction; the direction of reactions of these surface species depends on the hydrogen excess and also on the structure of starting hydrocarbon.
Based on the diploma work of Mr. M. Räth and Ms. B. Brose. 相似文献
EUROPT-1 , . , . , .
Based on the diploma work of Mr. M. Räth and Ms. B. Brose. 相似文献
908.
The efficient utilization of carbon dioxide (CO2) as a C1 feedstock is of great significance for green and sustainable development. Therefore, the efficient chemical conversion of CO2 into value-added products has recently attracted a lot of research attention in recent years. The transformation of CO2 generally requires high-energy substrates, specific catalysts, and harsh reaction conditions due to its high thermodynamic stability and kinetic inertness. Consequently, several efforts have been dedicated toward the development of high-performance catalysts and new reaction routes for CO2 conversion over the last few decades. To date, many routes of convert CO2 into value-added chemicals have been proposed, together with the development of heterogeneous and homogeneous catalysts. Among the advanced catalysts reported to date, ionic liquids (ILs) have been widely investigated and show great potential for the efficient, selective, and economical conversion of CO2 into highly valuable products under mild conditions, even under ambient conditions. Some task-specific ILs have been designed with unique functional groups (e.g., —OH, —SO3H, —NH2, —COOH, and —C≡N), which can act as the solvent, absorbent, activating agent, catalyst, or cocatalyst to realize the transformation of CO2 under metal-free and mild conditions. In addition, a variety of catalytic systems composed of ILs and metal catalysts have also been reported for the transformation of CO2, in which the combination of the IL and metal catalyst is responsible for CO2 conversion with high efficiency. In this review article, we summarize the recent advances in IL-mediated CO2 transformation into chemicals prepared via C—O, C—N, C—S, C—H, and C—C bond forming processes. ILs that can chemically capture CO2 with high capacity are first introduced, which can activate CO2 via the formation of IL-based carbonates or carbamates, thus realizing the transformation of CO2 under metal-free and mild conditions. Recent progress in IL-mediated CO2 transformations to form carbonates and various kinds of N- and S-containing compounds (e.g., oxazolidinones, ureas, benzimidazolones, formamides, methylamines, benzothiazoles, and other chemicals) as well as CO2 hydrogenation to give formic acid, methane, acetic acid, low-carbon alcohols, and hydrocarbons has been summarized in this review with a focus on the reaction routes, catalytic systems, and reaction mechanism. In these reactions, ILs can simultaneously activate the substrate via strong H-bonding in addition to activating CO2, and the cooperative effects among the ionic and molecular species and metal catalysts accomplish the reactions of CO2 with various kinds of substrates to afford a wide range of value-added chemicals. Finally, the shortcomings and perspectives of ILs are discussed. In short, IL-mediated CO2 transformations provide green and effective routes for the synthesis of high-value chemicals, which may have great potential for a wide range of applications. 相似文献
909.
Effects of double substitution on the thermodynamic stabilities of nitrogen radicals 总被引:1,自引:0,他引:1
Studiesonkineticsofradicalreactions[1]andonCHbonddissociationenergies(BDE)[2]haveshownthatcarbonradicalsarestabilizedbyeitheranelectrondonatinggroup(EDG)oranelectronwithdrawinggroup(EWG),andthatifacarbonradicalissubstitutedwithbothanEDGandanEWGatthesamecen… 相似文献
910.
Mesoporous molecular sieves were synthesized from Beta and Fau zeolite precursors through S+X−I+ route under extremely acidic conditions in parallel (designated as MBeta and MFau, respectively). The textural properties of MFau were different from its MBeta counterpart but resembled normal MCM-41 silica from TEOS. Al content in MBeta was almost equivalent to that in the initial Beta zeolite precursors, whereas only trace Al species was present in MFau from elemental analysis results. The hydrothermal stability of MBeta after post-synthesis ammonia treatment was considerably improved compared with normal MCM-41 aluminosilicates, whereas the MFau after the same procedure was as unstable as normal MCM-41 silica. Thus, the assembly behaviors of Beta and Fau zeolite precursors were comparatively studied based on these results. The microstructure of Fau zeolite precursors were degraded by the extremely acidic condition, and Al species was dissolved into the synthesis mixture. However, Beta zeolite precursors survived the chemical attack of extremely acidic media and were incorporated into mesostructured framework as primary building units. 相似文献