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991.
FengHui Tian ChengBu Liu Dongju Zhang Aiping Fu Yunbo Duan Shuping Yuan Jimmy C. Yu 《Chemphyschem》2010,11(15):3269-3272
Plane‐wave‐based pseudopotential density functional theory (DFT) calculations are used to elucidate the origin of the high photocatalytic efficiency of carbonate‐doped TiO2. Two geometrically possible doping positions are considered, including interstitial and substitutional carbon atoms on Ti sites. From the optical absorption properties calculations, we believe that the formation of carbonates after doping with interstitial carbon atoms is crucial, whereas the contribution from the cationic doping on Ti sites is negligible. The carbonate species doped TiO2 exhibits excellent absorption in the visible‐light region of 400–800 nm, in good agreement with experimental observations. Electronic structure analysis shows that the carbonate species introduce an impurity state from Ti 3d below the conduction band. Excitations from the impurity state to the conduction band may be responsible for the high visible‐light activity of the carbon doped TiO2 materials. 相似文献
992.
Jayaprakash KN Peng CG Butler D Varghese JP Maier MA Rajeev KG Manoharan M 《Organic letters》2010,12(23):5410-5413
Novel non-nucleoside alkyne monomers compatible with oligonucleotide synthesis were designed, synthesized, and efficiently incorporated into RNA and RNA analogues during solid-phase synthesis. These modifications allowed site-specific conjugation of ligands to the RNA oligonucleotides through copper-assisted (CuAAC) and copper-free strain-promoted azide-alkyne cycloaddition (SPAAC) reactions. The SPAAC click reactions of cyclooctyne-oligonucleotides with various classes of azido-functionalized ligands in solution phase and on solid phase were efficient and quantitative and occurred under mild reaction conditions. The SPAAC reaction provides a method for the synthesis of oligonucleotide-ligand conjugates uncontaminated with copper ions. 相似文献
993.
Xiao‐Chi Ma Xiulan Xin Bao‐jing Zhang Sha Deng Ji‐hong Yao Chang‐yuan Wang Jian Cui Yan Tian Ke‐xin Liu 《Journal of separation science》2010,33(15):2272-2277
An efficient separation method of using high‐speed counter‐current chromatography was successfully established to directly purify cytotoxic transformed products of cinobufagin by Cordyceps militaris. The two‐phase solvent system composed of n‐hexane–ethyl acetate–methanol–water (4:6:3:4, v/v) was used in high‐speed counter‐current chromatography. A total of 9 mg of 4β,12α‐dihydroxyl‐cinobufagin ( 1 ), 15 mg of 12β‐hydroxyl‐cinobufagin ( 2 ), 8 mg of 5β‐hydroxyl‐cinobufagin ( 3 ), 12 mg of deacetylcinobufagin ( 4 ) and 6 mg of 3‐keto‐cinobufagin ( 5 ) were obtained in a one‐step separation from 400 mg of the crude extract with purity of 98.7, 97.2, 90.6, 99.1 and 99.4%, respectively, as determined by HPLC. Their chemical structures were identified on the basis of 1H‐NMR and 13C‐NMR technology. All products ( 1 – 5 ) showed the potent activities against human carcinoma cervicis (Hela) and malignant melanoma (A375) cells in vitro. 相似文献
994.
A practical procedure has been developed for γ-oxygenation of α,β-unsaturated esters by a vinylogous O-nitroso Mukaiyama aldol reaction followed by a one-pot N-O bond heterolysis of the in situ generated γ-aminoxy-α,β-unsaturated esters. 相似文献
995.
Yuguang Jin Yanqing Tian Weiwen Zhang Sei-Hum Jang Alex K.-Y. Jen Deirdre R. Meldrum 《Analytical and bioanalytical chemistry》2010,398(3):1375-1384
The relationship between bacteria and host phagocytic cells is key to the induction of immunity. To visualize and monitor
bacterial infection, we developed a novel bacterial membrane permeable pH sensor for the noninvasive monitoring of bacterial
entry into murine macrophages. The pH sensor was constructed using 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran
(TCF) as an electron-withdrawing group and aniline as an electron-donating group. A piperazine moiety was used as the pH-sensitive
group. Because of the strong electron-donating and -withdrawing units conjugated in the sensing moiety M, the fluorophore
emitted in the red spectral window, away from the autofluorescence regions of the bacteria. Following the engulfment of sensor-labeled
bacteria by macrophages and their subsequent merger with host lysosomes, the resulting low-pH environment enhances the fluorescence
intensity of the pH sensors inside the bacteria. Time-lapse analysis of the fluorescent intensity suggested significant heterogeneity
of bacterial uptake among macrophages. In addition, qRT-PCR analysis of the bacterial 16 S rRNA gene expression within single
macrophage cells suggested that the 16 S rRNA of the bacteria was still intact 120 min after they had been engulfed by macrophages.
A toxicity assay showed that the pH sensor has no cytotoxicity towards either E. coli or murine macrophages. The sensor shows good repeatability, a long lifetime, and a fast response to pH changes, and can be
used for a variety of bacteria. 相似文献
996.
997.
Qiong Liu Xueying Liang Decong Hu Ping Chen Jing Tian Hong Zhang 《Frontiers of Chemistry in China》2010,5(1):88-98
Selenium (Se) is an essential trace element in vivo involved in the defense against oxidative stress. Se deficiency is associated with many human diseases. The bioactivity of
Se is dose- and species-dependent. Silkworm pupa has been reported to accumulate Se mainly in proteins. Thus the characterization
of major Se-containing proteins is very important in the application of Se-rich silkworm pupas in food and drugs. In this
study, crude proteins were extracted from Se-rich silkworm pupas, followed by DEAE-Sepharose and Sephedex G-75 chromatography.
Se content was measured after each step to determine the highest Se-containing fraction for the next step of separation. The
proteins obtained were analyzed using SDS-PAGE, followed by in-gel digestion with trypsin, and were characterized by MALDI-TOF
MS and ESI-MS/MS. These data showed two proteins mainly accumulated Se in the silkworm pupas. Those two proteins were proven
by mass spectrometry to be arylphorin and sex-specific storage-protein 2 precursor (SP-2), respectively. Both of them belong
to the storage proteins of amino acids during metamorphosis and the non-feeding pupal stage. The results suggest that Se could
be enriched by storage proteins and be supplied to silkworm pupas in accompany with amino acids for the synthesis of new Se-containing
proteins and peptides. 相似文献
998.
Kuilin Deng Haibin Zhong Xiangyang Zheng Xiaohui Song Hua Tian Pengfei Zhang Xiaobo Ren Haijun Wang 《先进技术聚合物》2010,21(8):584-590
In this study, a novel thermo‐sensitive poly(N‐acryloylglycinates) was prepared in order to get a potential drug release carrier. The corresponding monomers and the polymers were characterized with Fourier‐transform infrared (FTIR) and 1H NMR. The thermo‐sensitivity of the poly(N‐acryloylglycinates) was evaluated by measuring their lower critical solution temperatures (LCST) in water, inorganic salt solution, and different pH solutions. The results indicated that poly(N‐acryloylglycine methyl ester) (NAGME) and poly(N‐acryloylglycine ethyl ester) (NAGEE) exhibit a reversible thermo‐sensibility in their aqueous solutions at 61.5 and 12.5°C, respectively. However, no thermo‐sensitive behavior of poly(N‐acryloylglycine propyl ester) (NAGPE) was found due to its over hydrophobicity. The swelling studies on hydrogels were carried out at different temperatures, in different pH, and inorganic salt solutions. The hydrogels showed a remarkable phase transition at about 35°C with changing temperature. The release rate of caffeine from the thermo‐sensitive hydrogel was apparently decreased as the crosslinker content increased and temperature decreased. Seventy five percent caffeine from the polymeric hydrogel with 5% NMBA (N, N‐methylenebis(acrylamide)) was released at room temperature within 240 min, whereas 95.4% caffeine diffused into the medium at 37°C. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
999.
A new zinc phosphite (C2H8N2)0.5(HPO3)Zn has been hydrothermally synthesized from a mixture of ZnO, H3PO3, 4,4’-bipyridine, ethylenediamine, and H2O. Single-crystal X-ray diffraction analysis reveals that the Zn ions are first interconnected by HPO3 2- ligands to produce a neutrally infinite two-dimensional inorganic layer with four- and eight-membered rings, which is further used as the second building units and helically pillared by bridging ethylenediamine molecules to form the scarcely reported three-dimensional pillared-layer hybrid zinc phosphite with double-helical channels due to the flexibility of the ethylenediamine ligands. 相似文献
1000.
A new stationary phase based on silica modified with 1-methyl-3-propylimidazolium chloride was synthesized and characterized
in this paper. A derivative of 1-methyl-3-propylimidazolium chloride was used to chemically modify the surface of silica particles
to act as the stationary phase for HPLC. The modified particles were characterized by Fourier Transform Infrared (FT-IR), 13C NMR spectroscopy and thermogravimetric analysis (TGA). The surface modification procedure rendered particles with a surface
coverage of 0.89 μmol/m2 of alkylimidazolium chloride. Columns packed with the modified silica and blank silica particles were tested under HPLC conditions.
Preliminary evaluation of the stationary phase for HPLC was performed using aromatic compounds as model compounds. The separation
mechanism appears to involve multiple interactions including ion exchange, hydrophobic and electrostatic interactions. 相似文献