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51.
Won Sick Woo Sam Sik Kang Otto Seligmann V. Mohan Chari Hildebert Wagner 《Tetrahedron letters》1980,21(44):4255-4258
From the seeds of Phytolacca americana two new lignans, Americanin B and D, have been isolated and their structures elucidated mainly by spectroscopic methods 相似文献
52.
Chai OH Lee HK Lee YC Lee MS Han EH Kim HT Song CH 《Experimental & molecular medicine》2005,37(5):408-417
Trimellitic anhydride (TMA) is widely used industrially to make epoxy and alkyd resins, plasticizers and surfactants. The purpose of this study was to investigate whether contact hypersensitivity (CHS) is induced by repeated TMA challenge and the role of TNF-alpha and IgE in the TMA-induced CHS. The repetition of the challenge enlarged the extent of an early and a late phase of CHS in TNF-alpha+/+ (B6129SF2/J) and Balb/c mice. In the late phase of TMA-induced CHS, the peak of ear swelling responses by single challenge showed at 24 h after challenge, but the peak was observed at 8 h after repeated challenge. In the TNF-alpha knockout TNF-alpha-/- (B6;129S-Tnftm1Gk1) mice, the repetition of the TMA challenges enlarged the extent of the late phase of CHS, but less than those in TNF-alpha+/+ mice. Injection of anti-TNF-alpha antibody into the peritoneal cavity of Balb/c mice significantly decreased the extent of the late phase of CHS. Subcutaneous injection of anti-IgE antibody into Balb/c mice also decreased the extent of the late phase of CHS in dose-dependent manner. Histologically, infiltration of polymorphonuclear leukocytes and eosinophils was more pronounced in repeatedly TMA-challenged TNF-alpha+/+ and Balb/c mice than in the TNF-alpha-/- mice and anti-TNF-alpha or anti-IgE antibodies treated Balb/c mice. These results indicate that mice sensitized by TMA could possibly offer a useful model to study the mechanism of CHS, and TNF-alpha and IgE may act as potential modulators in the late phase of TMA-induced CHS. Neutralization of TNF-alpha and IgE by anti-TNF-alpha or anti-IgE antibodies may provide therapeutic tools for the treatment of TMA-induced CHS. 相似文献
53.
[reaction: see text]. Highly enantioenriched quaternary centers are obtained by the reaction of chiral lithiated intermediates complexed to (-)-sparteine with tetrasubstituted, alpha,alpha-dinitrile activated olefins. Lithiated N-Boc-N-Aryl benzylamine furnishes products with drs from 78:22 to 95:5, with ers exceeding 94:6. Lithiated N-Boc-N-Aryl allylamine reactants provide enecarbamate products with drs from 55:45 to 99:1, with ers ranging from 87:13 to 97:3. 相似文献
54.
Glypican-3 (GPC3) encodes a cell-surface heparan- sulfate proteoglycan and its expression is frequently silenced in ovarian cancer, mesotheliomas, and breast cancer cell lines and ectopic expression of GPC3 inhibited the growth of these cells, suggesting that GPC3 plays a negative role in cell proliferation. In contrast, up-regulation of GPC3 is often observed in hepatoma, neuroblastoma, and Wilms' tumor. Whether GPC3 plays the same growth inhibitory role in these tumors remains to be studied. Here we report that antisense-mediated knockdown of GPC3 in the HepG2 hepatoma cells significantly promotes the growth of hepatoma cells. In addition, we show that this growth promotion is independent of insulin-like growth factor 2 (IGF2) signaling. Our data suggest that GPC3 plays a growth-suppressing role in hepatoma and provide cell biological evidence inconsistent with the hypothesis that GPC3 acts as a growth suppressor by downregulating IGF2. 相似文献
55.
Hyung Kyu Shin 《Chemical physics letters》1976,37(1):143-146
A semiclassical approach is developed to study vibrational energy transfer in H2 + He by use of the a priori interaction potential including all nonzero impact parameter collisions. The calculated values of the rate coefficient are found to be in excellent agreement with experimental data which are available in the temperature ranges 60–450 K and 1350-3000 K. The temperature dependence is shown to seriously deviate from the Landau-Teller prediction below 1000 K. The calculation was carried out over the temperature range of 30 to 10000 K. 相似文献
56.
Pyun DK Kim BJ Jung HJ Kim JH Lee JS Lee WK Lee CH 《Chemical & pharmaceutical bulletin》2002,50(3):415-418
A new series of 1beta-methylcarbapenems 1a-d bearing 5-methyl-4-mercaptopyrrolidinone rings has been prepared and evaluated for in vitro antibacterial activity and pharmacokinetic parameters. Most compounds showed excellent antibacterial activity and high stability to dehydropeptidase-1. We have synthesized optically active 5-methyl-4-hydroxypyrrolidinones from enantiomerically pure aziridine esters. 相似文献
57.
Zhao X Gorelikov I Musikhin S Cauchi S Sukhovatkin V Sargent EH Kumacheva E 《Langmuir : the ACS journal of surfaces and colloids》2005,21(3):1086-1090
Thiol-capped water-soluble PbS nanocrystals (NCs) stabilized with 1-thioglycerol, dithioglycerol, or a mixture of 1-thioglycerol/dithioglycerol (TGL/DTG) were prepared via one-stage synthesis at room temperature. We found that NCs stabilized with a TGL/DTG mixture show efficient and stable infrared photoluminescence centered in the second "biological window" (1050-1200 nm). Under optimized conditions, full width at half-maximum of the PL emission peak was from 70 to 100 nm. PbS NCs were stable to precipitation and aggregation for the time period from 2 to 3 months when stored in the dark under room temperature. Room-temperature photoluminescence quantum efficiency of NCs was from 7 to 10%. When NCs were stored at 37 degrees C, their PL emission red-shifted, consistent with the NC growth. 相似文献
58.
Dong Won Kim Young Shin Jeon Young Kyu Jeong Moo Yul Suh Kih Soo Joe 《Journal of Radioanalytical and Nuclear Chemistry》1995,189(2):219-227
The chromatographic separation of lithium isotopes was investigated by chemical exchange with the recently synthesized polymer-bound dibenzo pyridino diamide azacrown (DBPDA) and reduced dibenzo pyridino diamide azacrown (RDBPDA). Column chromatography was employed for the determination of the effect of solvents and ligand conformation on the separation coefficients. The maximum separation coefficients, , for the DBPDA and RDBPDA at 20.0±0.02°C with acetonitrile as eluent, were found to be 0.034±0.002 and 0.035±0.002, respectively. The isotope separation coefficient and adsorption capability of the lithium ion on the DBPDA and RDBPDA were only slightly dependent on ligand structure, but strongly dependent on the solvent. DBPDA and RDBPDA appeared to have almost the same value for the isotope separation coefficient of lithium. 相似文献
59.
Jung-Hoon Oh Mun-Chual Rho Hyeong Kyu Lee Jae Nyoung Kim Sang-Hun Jung 《Tetrahedron letters》2004,45(38):7077-7079
Asymmetric synthesis of four possible stereoisomers of (9,10)-epoxyheptadecan-4,6-diyn-3-one was accomplished, and the absolute configuration of the naturally occurring (9R,10S)-epoxyheptadecan-4,6-diyn-3-one (1) was elucidated. 相似文献
60.
Yu-Ping Zhang Kwang-Pill Lee Hyun-Joo Noh Ali Md Showkat Seong-Ho Choi 《Microchemical Journal》2004,78(2):99-106
An appropriate optimization strategy should be used to find a desired resolution or selectivity with a minimum number of experiments in a limited time, which could assure the baseline separation of all target compounds. It was usually realized by means of a specialized computer program. In this paper, mapping optimization method and overlapping resolution mapping were compared for the optimization of a reversed-phase high-performance liquid chromatography (HPLC) isocratic separation of neutral compounds. The calculated resolutions and separation time of 7 to 10 experiments are fitted by different equations, which were used to build a contour plot with a minimum effective resolution and maximum retention time as a function of a mobile phase composition. The balance between resolution and analysis time could be easily realized by the overlapping of the final overlapping resolution mapping and analysis time mapping. The validity of the two methods was confirmed by some typical experiments. The models are simple, visual, and common without theoretical arithmetic. 相似文献