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251.
Chapman E Ding S Schultz PG Wong CH 《Journal of the American Chemical Society》2002,124(49):14524-14525
In the present work, we have used a newly developed, fluorescence-based assay to screen a library of >30 000 compounds as potential beta-arylsulfotransferase-IV inhibitors. A total of 11 inhibitors were discovered. Most of the compounds discovered showed low micromolar inhibition, but one of the compounds showed potent inhibition (Ki = 96 nM). The most potent of these inhibitors was tested against a variety of other purine binding enzymes and showed remarkable specificity. 相似文献
252.
253.
Hong‐Ze Gao Zhong‐Min Su Chun‐Sheng Qin Ri‐Gen Mo Yu‐He Kan 《International journal of quantum chemistry》2004,97(6):992-1001
Bis(2‐methyl‐8‐quinolinolato)aluminum(III) hydroxide complex (AlMq2OH) is used in organic light‐emitting diodes (OLEDs) as an electron transport material and emitting layer. By means of ab initio Hartree–Fock (HF) and density functional theory (DFT) B3LYP methods, the structure of AlMq2OH was optimized. The frontier molecular orbital characteristics and energy levels of AlMq2OH have been analyzed systematically to study the electronic transition mechanism in AlMq2OH. For comparison and calibration, bis(8‐quinolinolato)aluminum(III) hydroxide complex (Alq2OH) has also been examined with these methods using the same basis sets. The lowest singlet excited state (S1) of AlMq2OH has been studied by the singles configuration interaction (CIS) method and time‐dependent DFT (TD‐DFT) using a hybrid functional, B3‐LYP, and the 6‐31G* basis set. The lowest singlet electronic transition (S0 → S1) of AlMq2OH is π → π* electronic transitions and primarily localized on the different quinolate ligands. The emission of AlMq2OH is due to the electron transitions from a phenoxide donor to a pyridyl acceptor from another quinolate ligand including C → C and O → N transference. Two possible electron transfer pathways are presented, one by carbon, oxygen, and nitrogen atoms and the other via metal cation Al3+. The comparison between the CIS‐optimized excited‐state structure with the HF ground‐state structure indicates that the geometric shift is mainly confined to the one quinolate and these changes can be easily understood in terms of the nodal patterns of the highest occupied and lowest unoccupied molecular orbitals. On the basis of the CIS‐optimized structure of the excited state, TD‐B3‐LYP calculations predict an emission wavelength of 499.78 nm. An absorption wavelength at 380.79 nm on the optimized structure of B3LYP/6‐31G* was predicted. They are comparable to AlMq2OH 485 and 390 nm observed experimentally for photoluminescence and UV‐vis absorption spectra of AlMq2OH solid thin film on quartz, respectively. Lending theoretical corroboration to recent experimental observations and supposition, the reasons for the blue‐shift of AlMq2OH were revealed. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004 相似文献
254.
The 1,3,4,6‐tetra‐O‐acetyl‐2‐azido‐2‐deoxy‐β‐D ‐mannopyranose ( 4 ) or the mixture of 1,3,6‐tri‐O‐acetyl‐2‐azido‐2‐deoxy‐4‐O‐(2,3,4,6‐tetra‐O‐acetyl‐β‐D ‐galactopyranosyl)‐β‐D ‐mannopyranose ( 10 ) and the corresponding α‐D ‐glucopyranose‐type glycosyl donor 9 / 10 reacted at room temperature with protected nucleosides 12 – 15 in CH2Cl2 solution in the presence of BF3?OEt2 as promoter to give 5′‐O‐(2‐azido‐2‐deoxy‐α‐D ‐glycosyl)nucleosides in reasonable yields (Schemes 2 and 3). Only the 5′‐O‐(α‐D ‐mannopyranosyl)nucleosides were obtained. Compounds 21, 28, 30 , and 31 showed growth inhibition of HeLa cells and hepatoma Bel‐7402 cells at a concentration of 10 μM in vitro. 相似文献
255.
Studyofthegrowthprocessofcolloidalparticlesofnonequilibriumandirreversibilityisanactiveareaofresearch.Therecognitionofcolloidalaggregatesasfractalobjectshasinspiredalargenumberofexperimentalandtheoreticalstudiesonthestructuralandkineticaspectsofaggregationprocesses"'.Morerecently,kineticsofhematiteaggregationbypolyacrylicacidhavebeenstudiedbyzhangandBume3.Theprimaryhematiteparticleswerequiteuniformandfairlyspherical.Inthispaper,wewillreportthesizeevolutionoffractalaggregatesofinitiallypolydis… 相似文献
256.
IntroductionInthepasttwodecades ,alargefamilyofnaturalproductsnamedannonaceousacetogeninswereisolatedandcharacterizedbytheglobalresearchersfromvariousspeciesoftheplantannonaeae .1Amongover 4 0 0mem bers,mostofthemwerefoundtoshowpotentcytotoxicandantitumora… 相似文献
257.
Rong-Bin Huang Chun-Ru Wang Zhao-Yang Liu Lan-Sun Zheng Fei Qi Liu-Si Sheng Shu-Qin Yu Yun-Wu Zhang 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1995,33(1):49-52
A series of cluster anions C n X? are produced from laser ablation of appropriate samples, where X is selected as a group-VB element. The recorded mass spectra of these cluster anions display a drastic even/odd alternation on ion intensities: For C n N?, only anions with oddn can be observed; For C n P? and C n As?, cluster anions with evenn are produced but with lower signal intensities; For C n Sb?, the signal intensity of clusters does not show even/odd alternation; Finally, for C n Bi?, the intensities of cluster anions with evenn are higher than those with oddn. This parity effect can be attributed to the linear structure of the cluster anions, and the parity reversal of C n X? from C n N? to C n Bi? can be explained from the electronegativity decreasing of the heteroatom X as it descends in the group. The Hückel model was applied to account the structural feature of these clusters. 相似文献
258.
Hui‐yi Lin Chung‐Hsiung Chen KarinC.S. ChenLiu Shoei‐Sheng Lee 《Helvetica chimica acta》2003,86(1):127-138
Six 14‐membered cyclopeptide alkaloids, i.e., ramosines A–C, mucronine J, and lotusines A and D, were isolated from the roots of Paliurus ramosissimus, and an additional four, hemsines A–D, from the roots of P. hemsleyanus. Among these, ramosines A–C ( 1, 5 , and 6 , resp.) and hemsines A and B ( 7 and 8 , resp.) are new bases of the amphibine‐B type, and hemsines C and D ( 9 and 10 , resp.) are new integerrine‐type alkaloids. Additionally, ramosine C ( 6 ) represents the first 14‐membered cyclopeptide alkaloid possessing a substitution (? OH) at C(13′). Their structural elucidations were based on spectral analysis and molecular‐modeling studies. Pronounced solvent effects in the 1H‐ and 13C‐NMR spectra of these two types of alkaloids were observed. 相似文献
259.
T. L. Wang H. W. Tong X. Y. Yan L. Q. Sheng J. Yang S. M. Liu 《Chromatographia》2005,62(11-12):631-636
An effective and rapid method, use of a 2,4-dinitrophenylhydrazine (DNPH)-treated Cambridge filter and high-performance liquid chromatography (HPLC) with diode-array detection (DAD), has been used for determination of low-molecular-mass carbonyl compounds in cigarette smoke. Different chromatographic mobile phases were investigated and the optimized mobile phase was a gradient prepared from water–acetonitrile–tetrahydrofuran (THF)–iso-propanol, 59:30:10:1 (v/v) (mixture A) and acetonitrile–water, 65:35 (v/v) (mixture B). Under the optimized chromatographic conditions, the 2,4-dinitrophenylhydrazones of formaldehyde, acetaldehyde, acrolein, acetone, propionaldehyde, 2-butanone, and iso-butyraldehyde were separated completely in an 18 min chromatographic run. The concentration of acid, which has large effect on carbonyl-DNPH derivatization, was investigated by adding different volumes of perchloric acid. The DNPH-treated Cambridge filter was convenient and effective compared with conventional methods used to collect and derivatize the carbonyl compounds present in cigarette smoke. Validation of the method showed it to be effective, precise, accurate, and linear over the range of concentrations of analyzed. 相似文献
260.
Wei Jiang Hongping Li Sheng Yin Xin Wang Wei Liu Hui Liu Wenshuai Zhu Huaming Li 《应用有机金属化学》2016,30(9):753-758
Two hexacyanoferrate‐based ionic liquids, [C4Py]3Fe(CN)6 and [C16Py]3Fe(CN)6, were synthesized and characterized using Fourier transform infrared and mass spectroscopies and CHN analysis. They were employed as Fenton‐like catalysts in extraction and catalytic oxidative desulfurization of model oil with dibenzothiophene (DBT), benzothiophene (BT), 4,6‐dimethyldibenzothiophene (4,6‐DMDBT), 4‐methyldibenzothiophene (4‐MDBT) and 3‐methylbenzothiophene (3‐MBT) as substrates. Various polar solvents, such as ionic liquids, water and organic solvents, were applied to choose a suitable extractant. The results showed the removal of DBT reached 97.1% with [C4Py]3Fe(CN)6 as a catalyst and 1‐n‐octyl‐3‐methylimidazolium hexafluorophosphate ([C8mim]PF6) as an extractant under optimal conditions. The activity of sulfur removal followed the order DBT > 3‐MBT > BT > 4‐MDBT >4,6‐DMDBT. The effect of water content on sulfur removal was investigated by adding various concentrations of H2O2. It was found that excess water had a positive effect on sulfur removal but the catalysts were less sensitive than [FeCl4?]‐based catalysts to water. The mechanism was studied using electron spin‐resonance spectroscopy and gas chromatography–mass spectrometry. O2?? may be the active oxygen species in the catalytic oxidative desulfurization process and the oxidation products of various sulfur compounds were the corresponding sulfoxides and sulfones. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献