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991.
Lv J Zhang L Hu S Cheng JP Luo S 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(3):799-803
Remote F effect: Unprecedented hetero-Diels-Alder reactions of mono- and bis-substituted cyclopentadienes have been realized by an asymmetric binary-acid catalyst that synergistically combines a chiral phosphoric acid 1?h/InBr(3) with good periselectivity, high regioselectivity, and excellent stereoselectivity. Substituent mapping of the chiral phosphoric acid indicates a dramatic remote ortho-fluoro effect on the stereocontrol. 相似文献
992.
993.
994.
Bao-Sheng Liu Chun-Li Xue Jing Wang Chao Yang Yun-Kai Lv 《Monatshefte für Chemie / Chemical Monthly》2012,37(3):203-209
Abstract
Ponceau S (PS) can quench the fluorescence of bovine serum albumin (BSA) in aqueous solution of pH 7.40. The static fluorescence-quenching process between BSA and PS was confirmed and the binding constant, the number of binding sites, and thermodynamic data for the interaction between BSA and PS were obtained. The results showed that the number of binding sites was 1 and that electrostatic attraction was important in the binding of BSA to PS. On the basis of the theory of F?rster resonance energy transfer, the binding distance (r < 7 nm) between PS and BSA was obtained. Site marker competitive experiments indicated that binding of PS to BSA primarily occurred in sub-domain IIA (site I). There was no obvious fluorescence intensity change on combining BSA and gentamicin (GM), so the conjugation reaction between BSA and GM cannot be studied by spectroscopy. It was observed that when GM was added to the BSA–PS system, the relative fluorescence intensity of the system recovered gradually with increasing concentration of GM, which showed there was a conjugation reaction between GM and BSA and that binding of GM to BSA primarily occurred in sub-domain IIA (site I). 相似文献995.
Yaping Tian Jiuming HeRuiping Zhang Haining Lv Shuanggang MaYanhua Chen Shishan YuXiaoguang Chen Yan WuWenyi He Zeper Abliz 《Analytica chimica acta》2012
An integrated approach combining data acquisition using MSE and multi-period product ion scan (mpMS/MS), with high-resolution characteristic extracted ion chromatograms (hcXIC) as a data mining method, was developed for in vivo drug metabolites screening and identification. This approach is illustrated by analyzing metabolites of a potential anticancer agent, 3,6,7-trimethoxyphenanthroindolizidine (CAT) in rat urine based on rapid resolution liquid chromatography combined with tandem mass spectrometry (RRLC–MS/MS). Untargeted full-scan MSE enabled the high-throughput acquisition of potential metabolites, and targeted mpMS/MS contributed to the sensitivity and specificity of the acquisition of molecules of interest. The data processing method hcXIC, based on the structure of CAT, was shown to be highly effective for the metabolite discovery. Through the double-filtering effect of the characteristic ion and accurate mass, conventional extracted ion chromatograms that contained a substantial number of false-positive peaks were simplified into chromatograms essentially free of endogenous interferences. As a result, 21 metabolites were detected in rat urine after oral administration of CAT. Based on the characteristic fragmentation patterns of the phenanthroindolizidine alkaloid, the structures of 9 metabolites were identified. Furthermore, the interpretation of the MS/MS spectra of these metabolites enabled the determination of demethylation position as well as the differentiation between N-oxidized and hydroxylated metabolites. 相似文献
996.
O'Brien M Leach A Armstrong RJ Chong K Sheridan R 《Organic & biomolecular chemistry》2012,10(12):2392-2394
Utilising the propensity of the 2-furanyl group to facilitate equilibration of an adjacent tosylamide chiral centre, a diastereoselective route to 2,6-syn-piperidines was developed that proceeds with high levels of thermodynamic stereocontrol. X-ray crystallography structures suggest that, as seen in similar systems, pseudo-allylic strain between the N-tosyl group and the substituents at the 2 and 6 positions dominates stereochemical preference, overriding 1,3 diaxial interactions. 相似文献
997.
In this paper, we aim to answer the question proposed by Magdziarz (Stoch. Proc. Appl. 119:3238?C3252, 2009), i.e. we investigate the solution of an anomalous diffusion equation with time and space dependent force and diffusion coefficient. First, we try to find the stochastic representation of this equation, which means the PDF of this stochastic process is rightly the solution of the equation we aim to solve. Then, we also simulate the sample paths of the stochastic process. At last, taking advantage of the stochastic representation method, we employed Monte Carlo method to approximate the solution of the mentioned equation. 相似文献
998.
Lv Y Zhang H Cao Y Dong L Zhang L Yao K Gao F Dong L Chen Y 《Journal of colloid and interface science》2012,372(1):63-72
The dispersion and physicochemical behaviors of CuO-CoO binary metal oxides supported on γ-Al(2)O(3) were characterized by XRD, LRS, XPS, H(2)-TPR, and in situ FT-IR techniques. Their activities were evaluated by NO-CO model reaction. The results indicated that (a) for lower loadings, CuO and CoO were able to be highly dispersed on the surface of γ-Al(2)O(3) support; (b) the interaction between dispersed CuO and CoO upon γ-Al(2)O(3) was discussed in the view of incorporation model. According to this model and obtained results, the surface dispersed Cu-O-Co species were considered to exist on the surface of γ-Al(2)O(3); (c) CO or/and NO adsorption FT-IR results evidenced that the surface dispersed copper species could be reduced to lower valence by CO and the NO adsorption species converted with the increase in the temperature; (d) the surface dispersed Cu-O-Co species could be reduced to active Cu-□-Co species by CO among the mixture atmosphere. The formation of the surface synergetic oxygen vacancy (SSOV) was a crucial factor in the process of the NO-CO reaction. And a possible reaction pathway was tentatively proposed to discuss the NO-CO reaction based on all of these results. 相似文献
999.
1000.
A. Yili Q. L. Ma Q. Y. Lv Y. H. Gao B. Zhao O. N. Veshkurova Sh. I. Salikhov H. A. Aisa 《Chemistry of Natural Compounds》2012,48(4):643-645
Four peptides of molecular weights 1.148, 4.68, 5.41, and 9.086 kDa with antioxidant activity were isolated from chickpea
sprout using two-step ion-exchange chromatographic and HPLC techniques for the first time. The partial N-terminal amino acid
sequences of the peptide named YZDBCM-1 (9.086 kDa) was determined as H2N1-15-H2N-Ala-Ile-Thr-Cys-Gly-Arg-Val-Ser-Ala-Ala-Leu-Ala-Pro-Pro-Leu using the Edman automated sequencing apparatus, which was a
new peptide rich in alanine. It was shown that the antioxidant activity of the peptide YZDBCM-1 was IC50 156.2 μg/mL (17.2 μmol/L) to the free radical of ABTS. 相似文献