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排序方式: 共有308条查询结果,搜索用时 46 毫秒
101.
Tran L Choi SB Al-Najjar BO Yusuf M Wahab HA Le L 《Molecules (Basel, Switzerland)》2011,16(12):10227-10255
The M2 channel protein on the influenza A virus membrane has become the main target of the anti-flu drugs amantadine and rimantadine. The structure of the M2 channel proteins of the H3N2 (PDB code 2RLF) and 2009-H1N1 (Genbank accession number GQ385383) viruses may help researchers to solve the drug-resistant problem of these two adamantane-based drugs and develop more powerful new drugs against influenza A virus. In the present study, we searched for new M2 channel inhibitors through a combination of different computational methodologies, including virtual screening with docking and pharmacophore modeling. Virtual screening was performed to calculate the free energies of binding between receptor M2 channel proteins and 200 new designed ligands. After that, pharmacophore analysis was used to identify the important M2 protein-inhibitor interactions and common features of top binding compounds with M2 channel proteins. Finally, the two most potential compounds were determined as novel leads to inhibit M2 channel proteins in both H3N2 and 2009-H1N1 influenza A virus. 相似文献
102.
The methanol and fractionated extracts (hexane, ethyl acetate and water) of Alpinia mutica (Zingiberaceae) rhizomes were investigated for their cytotoxic effect against six human carcinoma cell lines, namely KB, MCF7, A549, Caski, HCT116, HT29 and non-human fibroblast cell line (MRC 5) using an in vitro cytotoxicity assay. The ethyl acetate extract possessed high inhibitory effect against KB, MCF7 and Caski cells (IC?? values of 9.4, 19.7 and 19.8 μg/mL, respectively). Flavokawin B (1), 5,6-dehydrokawain (2), pinostrobin chalcone (3) and alpinetin (4), isolated from the active ethyl acetate extract were also evaluated for their cytotoxic activity. Of these, pinostrobin chalcone (3) and alpinetin (4) were isolated from this plant for the first time. Pinostrobin chalcone (3) displayed very remarkable cytotoxic activity against the tested human cancer cells, such as KB, MCF7 and Caski cells (IC?? values of 6.2, 7.3 and 7.7 μg/mL, respectively). This is the first report of the cytotoxic activity of Alpinia mutica. 相似文献
103.
Krüger S Mögel HJ Wahab M Schiller P 《Langmuir : the ACS journal of surfaces and colloids》2011,27(2):646-650
A simple mathematical model for the depletion force between two arbitrarily shaped large convex colloidal particles immersed in a suspension of small spherical particles is proposed. Using differential geometry, the interaction potential is expressed in terms of the mean and Gaussian curvature of the particle surfaces. The accuracy of theoretical results is tested by Monte Carlo simulations for parallel and nonparallel circular cylinders. The agreement between theoretical results and simulated data is very good if the density of the depletion agent is not too high. 相似文献
104.
Omar NF Hassan SA Yusoff UK Abdullah NA Wahab PE Sinniah U 《Molecules (Basel, Switzerland)》2012,17(3):2378-2387
A field study was conducted to determine the effect of organic and mineral-based fertilizers on phytochemical contents in the tubers of two cassava varieties. Treatments were arranged in a split plot design with three replicates. The main plot was fertilizer source (vermicompost, empty fruit bunch compost and inorganic fertilizer) and sub-plot was cassava variety (Medan and Sri Pontian). The amount of fertilizer applied was based on 180 kg K(2)O ha-1. The tubers were harvested and analyzed for total flavonoids, total phenolics, antioxidant activity and cyanogenic glucoside content. Total phenolic and flavonoid compounds were determined using the Folin-Ciocalteu assay and aluminium chloride colorimetric method, respectively. Different sources of fertilizer, varieties and their interactions were found to have a significant effect on phytochemical content. The phenolic and flavonoid content were significantly higher (p < 0.01) in the vermicompost treatment compared to mineral fertilizer and EFB compost. The total flavonoids and phenolics content of vermicompost treated plants were 39% and 38% higher, respectively, than those chemically fertilized. The antioxidant activity determined using the DPPH and FRAP assays were high with application of organic fertilizer. Cyanogenic glycoside levels were decreased with the application of organic fertilizer. Among the two types of compost, vermicompost resulted in higher nutritional value of cassava tubers. Medan variety with application of vermicompost showed the most promising nutritional quality. Since the nutritional quality of cassava can be improved by organic fertilization, organic fertilizer should be used in place of chemical fertilizer for environmentally sustainable production of better quality cassava. 相似文献
105.
Zeid Abdullah Alothman Saikh Mohammad Wabaidur Mohammad Rizwan Khan Ayman Abdel Ghafar Mohamed Abdelaty Habila Yacine Badjah Hadj Ahmed 《Journal of separation science》2012,35(21):2892-2896
In the present work, a rapid and sensitive ultra performance liquid chromatography‐mass spectrometry method has been proposed for the analysis of capsaicinoids (nordihydrocapsaicin, capsaicin, dihydrocapsaicin, homocapsaicin, and homodihydrocapsaicin) present in different Capsicum samples. Extraction of capsaicinoids was carried out by liquid–liquid extraction using ethanol as an extracting solvent, while the chromatographic separation was achieved by reversed phase C18 column with gradient mobile phase (solvent A: acetonitrile and solvent B: water with 0.1% formic acid). Under the optimum experimental conditions, the linear ranges were 0.5–50 μg/g with correlation coefficient (r2) >0.999 for each capsaicinoids and detection limits were 0.15, 0.05, 0.06, 0.2, and 0.1 μg/g for nordihydrocapsaicin, capsaicin, dihydrocapsaicin, homocapsaicin, and homodihydrocapsaicin, respectively. Run‐to‐run and day‐to‐day precisions of the method with relative standard deviations <1.5% were achieved for all analyzed capsaicinoids. The robustness of the method was determined by utilizing different injection volumes of the extracts. Furthermore, to validate the system robustness, a run of high number of capsaicinoids present in different varieties of Capsicum samples was performed in this study. All the capsaicinoids were separated in a time of less than 9 min by employing the proposed method. 相似文献
106.
M. Asghar F. Iqbal S.M. Faraz V. Jokubavicius Q. Wahab M. Syväjärvi 《Physica B: Condensed Matter》2012,407(15):3038-3040
Deep level transient spectroscopy (DLTS) is employed to study deep level defects in n-6H-SiC (silicon carbide) epilayers grown by the sublimation method. To study the deep level defects in n-6H-SiC, we used as-grown, nitrogen doped and nitrogen-boron co-doped samples represented as ELS-1, ELS-11 and ELS-131 having net (ND–NA) ∼2.0×1012 cm−3, 2×1016 cm−3 and 9×1015 cm3, respectively. The DLTS measurements performed on ELS-1 and ELS-11 samples revealed three electron trap defects (A, B and C) having activation energies Ec – 0.39 eV, Ec – 0.67 eV and Ec – 0.91 eV, respectively. While DLTS spectra due to sample ELS-131 displayed only A level. This observation indicates that levels B and C in ELS-131 are compensated by boron and/or nitrogen–boron complex. A comparison with the published data revealed A, B and C to be E1/E2, Z1/Z2 and R levels, respectively. 相似文献
107.
Time dependent optogalvanic signals induced by the 1s4 → 2pj laser excitations have been studied in neon DC plasma. The decay rates related to all the four 1si levels have been derived by fitting the waveforms with a mathematical rate equation model. The temporal signatures of three transitions namely 638.3, 650.7 and 724.5 nm related to the 2p7, 2p8 and 2p10 upper levels, respectively, have been found to be different from the rest of the transitions. We relate these effects to the population redistribution of decaying channels and to the processes responsible for the optogalvanic effect. 相似文献
108.
Rizwan Wahab 《Applied Surface Science》2009,255(9):4891-4896
In this paper we present a systematic study on the morphological variation of ZnO nanostructure by varying the pH of precursor solution via solution method. Zinc acetate dihydrate and sodium hydroxide were used as a precursor, which was refluxed at 90 °C for an hour. The pH of the precursor solution (zinc acetate di hydrate) was increased from 6 to 12 by the controlled addition of sodium hydroxide (NaOH). Morphology of ZnO nanorods markedly varies from sheet-like (at pH 6) to rod-like structure of zinc oxide (pH 10-12). Diffraction patterns match well with standard ZnO at all pH values. Crystallinity and nanostructures were confirmed by high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) pattern, which indicates structure grew along [0 0 0 1] direction with an ideal lattice fringes distance 0.52 nm. FTIR spectroscopic measurement showed a standard peak of zinc oxide at 464 cm−1. Amount of H+ and OH− ions are found key to the structure control of studied material, as discussed in the growth mechanism. 相似文献
109.
Cheng‐Hao Liu Muhammad Rizwan Niazi Dmitrii F. Perepichka 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(48):17473-17482
π‐Conjugated organic materials possess a wide range of tunable optoelectronic properties which are dictated by their molecular structure and supramolecular arrangement. While many efforts have been put into tuning the molecular structure to achieve the desired properties, rational supramolecular control remains a challenge. Here, we report a novel series of supramolecular materials formed by the co‐assembly of weak π‐electron donor (indolo[2,3‐a]carbazole) and acceptor (aromatic o‐quinones) molecules via complementary hydrogen bonding. The resulting polarization creates a drastic perturbation of the molecular energy levels, causing strong charge transfer in the weak donor–acceptor pairs. This leads to a significant lowering (up to 1.5 eV) of the band gaps, intense absorption in the near‐IR region, very short π‐stacking distances (≥3.15 Å), and strong ESR signals in the co‐crystals. By varying the strength of the acceptor, the characteristics of the complexes can be tuned between intrinsic, gate‐, or light‐induced semiconductivity with a p‐type or ambipolar transport mechanism. 相似文献
110.
A rapid, high resolution, and low sample consumption CZE method is developed for peptide nucleic acid (PNA) analysis for the first time. 30% v/v acetonitrile in PNA sample and 20% v/v acetonitrile in 50 mM borax‐boric acid (pH 8.7) as BGE were employed after optimization. The calibration curves were linear for PNA concentration ranging from 1 to 50 μmol/L. LOD and LOQ of PNA were 0.2 and 1.0 μmol/L, respectively. Since the commercially available reagent gives rise to huge PNA peak and an apparent impurity peak, the purity of PNA was evaluated to be about 81.4% by CZE method, obviously lower than the supplier's purity value of 99.9% evaluated by RP–HPLC, and also lower than 94.8% determined with RP–HPLC by our research group. The CZE method takes only 5 min, needs only 90 nL PNA, much less than 20 min and 20 μL PNA in RP–HPLC method. Moreover, the CZE method is applicable for the analysis of glutamic acid modified and lysine modified PNAs, they show different migration time with their corresponding complementary PNAs. Our results show CZE provides a new choice for PNA and modified PNA analysis, also their purity or quality evaluation. 相似文献