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71.
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
72.
1,7-Enynes 1, connected through an aromatic ring and bearing a leaving methoxy group at the 4-position, underwent the PtBr(2)-catalyzed enyne metathesis followed by aromatization in one pot to afford vinyl naphthalenes 3 in good to acceptable yields. The cyclobutene intermediate 11a and another intermediate 2a were isolated, indicating that PtBr(2) acts as a dual role catalyst: (1) as a transition metal catalyst, it induces the enyne metathesis to produce 11a starting from 1a, and (2) as a Lewis acid catalyst, it facilitates elimination of MeOH from 2a to give the aromatized product 3a. 相似文献
73.
A new type of latex particle was prepared by copolymerization of styrene and poly(ethylene oxide) macromonomer. By controlling the concentration of styrene in reaction mixtures, several latexes with different grain sizes were obtained. The packing patterns of the latex films as well as shapes and sizes of the latex particles were measured with atomic force microscopy (AFM). AFM images revealed that the grain sizes of the latexes increase with increasing concentration of styrene. At a higher styrene concentration (10 wt%), the latex showed a rather homogenous distribution of grain sizes. Lateral force microscopy (LFM) was used to reveal frictional features of latex particles. Contact and non-contact mode AFM were employed to image the same sample of the latex films. The results show that AFM working in non-contact mode can be used to effectively eliminate the horizontal-line-like artifacts, which may obscure AFM images. 相似文献
74.
Jo‐Nan Chen Fang‐Ming Hsu Hui‐Chun Wang Chung‐Wen Wu Pao‐Swu Cheng Wen‐Liang Tsai 《中国化学会会志》2006,53(4):931-938
Four series of compounds 11?50 containing terminal alicyclic rings such as cyclohexylmethyl, cyclopentylmethyl, cyclobutylmethyl, and cyclopropylmethyl rings were synthesized and their liquid crystal behavior studied. The ring size and the length of flexible alkoxy chain influence the phase formation in different ways. While the smaller ring and the shorter alkoxy chain tend to favor the formation of the N phase, the larger ring and the longer alkoxy chain tend to favor the formation of the SmC phase. All the compounds except 11 and 21 exhibit SmA phases. The widest temperature range of the N, SmA, and SmC phases are found in the compounds 41 , 46 , and 20 , respectively, which are 75 °C for 41 , 115 °C for 46 , and 100 °C for 20 . 相似文献
75.
The interaction between gatifloxacin mesylate (GM) and salmon sperm DNA was studied by fluorescence spectrometry and ultra‐violet (UV) spectrometry. Additions of salmon sperm DNA to GM solution resulted in its strong fluorescence quenching and UV absorbance decrease due to the strong interaction between GM and salmon sperm DNA. Both the maximum fluorescence emission wavelength and the maximum UV absorbance wavelength of GM did not change with the increasing concentration of salmon sperm DNA, indicating no intercalative binding existed between them. The Stern‐Volmer plot indicated that the fluorescence‐quenching constant at different temperatures or different salmon sperm DNA concentration ranges was different. Effects of ionic strength and I? on the fluorescence quenching of GM by salmon sperm DNA indicated that electrostatic interaction and groove binding coexisted between them. 相似文献
76.
Direct electrochemical and electrocatalytic behavior of hemoglobin (Hb) immobilized on glass carbon electrode (GCE) containing gelatine (Gel) films was investigated. The characteristics of Hb/Gel film modified GC electrode were performed by using SEM microscopy, UV-vis spectroscopy and electrochemical methods. The immobilized Hb showed a couple of quasi-reversible redox peak with a formal potential of −0.38 V (versus SCE) in 0.1 M pH 7.0 PBS. The formal potential changed linearly from pH 4.03 to 8.41 with a slope value of −52.0 mV pH−1, which suggested that a proton transfer was accompanied with each electron transfer (ET) in the electrochemical reaction. The Hb/gelatine/GCE displayed a rapid amperometric response to the reduction of H2O2 and nitrite. 相似文献
77.
X射线荧光分析技术的研发动态 总被引:1,自引:0,他引:1
周南 《理化检验(化学分册)》2005,41(7):539-540
X射线荧光分析法(XRF)的正确命名,根据IUPAC命名委员会的建议,宜称作“X射线发射分析法”,因并不发生荧光,在保护环境的大前提下,它在分析化学中的地位日益受到重视。随着分析仪器向小型化发展的趋势,X射线荧光分析仪也向手提式轻便、小型携化发展,如手枪式或其他便于握持的式样。 相似文献
78.
A new method in which a series of substituted carbazoles is efficiently produced by the combination of an amide and an arene is described. The key feature of this method is the palladium-catalyzed tandem directed C-H functionalization and amide arylation. The method tolerates substitution on either ring of the biaryl amide substrates, and the products can be assembled in a simple two-step protocol from readily available reagents. The Pd(0) species generated are reoxidized to Pd(II) in the presence of Cu(OAc)2 and an atmosphere of oxygen. 相似文献
79.
A selective titrimetric determination of Pb after separation by a modified method of precipitation as its sulphate is proposed. Pb(II), present as the perchlorate, is precipitated by gentle boiling in 3.6M H(2)SO(4) presaturated with PbSO(4) and free from any extraneous anions. The customary time-consuming evaporation to fumes of sulphuric acid is dispensed with. The precipitate is collected, and dissolved in excess of HEDTA, the surplus of which is back-titrated with Zn(II) at pH 5.0-5.5. Use of Catechol Violet and Xylenol Orange as a mixed indicator gives a sharper end-point. The standard deviation of the proposed method for 60 mg of lead is 0.35 mg. The method has been successfully used to determine Pb in non-ferrous alloys. 相似文献
80.
Discharge performance of K2FeO4 electrode under different conditions was studied by the constant electric current discharge method. The electrochemical characteristics of K2FeO4 electrode were investigated for the first time by means of cyclic voltammetry. The results show that the K2FeO4 electrode made at moderate pressure (20MPa) and discharged at lower current has better discharge performance. It is also found that K2FeO4 electrode is significantly rechargeable. 相似文献