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排序方式: 共有109条查询结果,搜索用时 265 毫秒
31.
Nazia Bibi Sheraz Ahmad. K. Tanoli Sadia Farheen Nighat Afza Salman Siddiqi Ying Zhang Shahana U. Kazmi Abdul Malik 《Bioorganic & medicinal chemistry letters》2010,20(14):4173-4176
In vitro antituberculosis activities of fractions and pure compounds (1–20) including seven triterpenes, two alkaloids, two cycloheximide derivatives, two coumarins six sterol derivatives and a long chain alcohol, respectively, isolated from Haloxylon salicornicum were determined against Mycobecterium tuberculosis H37Rv. Actively growing cultures were tested by rapid colorimetric method while the stationary phase cultures were tested by drug exposure methods for bactericidal activity. The MIC values were found to be 50 μg/ml for compounds 15, 19 and 20 where as rest of the compounds invariably showed MIC value of 100 μg/ml against the logarithmic phase culture. These were compare to Isoniazid as a control drug. The compounds exhibited no activity against the stationary phase culture of M. tuberculosis H37Rv up to 200 μg/ml. Further studies are required to investigate the in vivo efficacies and activities of the compounds in combination with antimicrobials that are already being used for TB therapy. 相似文献
32.
Background
Alcoholism presents widespread social and human health problems. Alcohol sensitivity, the development of tolerance to alcohol and susceptibility to addiction vary in the population. Genetic factors that predispose to alcoholism remain largely unknown due to extensive genetic and environmental variation in human populations. Drosophila, however, allows studies on genetically identical individuals in controlled environments. Although addiction to alcohol has not been demonstrated in Drosophila, flies show responses to alcohol exposure that resemble human intoxication, including hyperactivity, loss of postural control, sedation, and exposure-dependent development of tolerance. 相似文献33.
Most bacteria in the ocean can be motile. Chemotaxis allows bacteria to detect nutrient gradients, and hence motility is believed to serve as a method of approaching sources of food. This picture is well established in a stagnant environment. In the ocean a shear microenvironment is associated with turbulence. This shear flow prevents clustering of bacteria around local nutrient sources if they swim in the commonly assumed "run-and-tumble" strategy. Recent observations, however, indicate a "back-and-forth" swimming behavior for marine bacteria. In a theoretical study we compare the two bacterial swimming strategies in a realistic ocean environment. The "back-and-forth" strategy is found to enable the bacteria to stay close to a nutrient source even under high shear. Furthermore, rotational diffusion driven by thermal noise can significantly enhance the efficiency of this strategy. The superiority of the "back-and-forth" strategy suggests that bacterial motility has a control function rather than an approach function under turbulent conditions. 相似文献
34.
The vibrational structure of the chromophore in the primary photoproduct of vision, bathorhodopsin, is examined to determine the cause of the anomalously decoupled and intense C(11)=C(12) hydrogen-out-of-plane (HOOP) wagging modes and their relation to energy storage in the primary photoproduct. Low-temperature (77 K) resonance Raman spectra of Glu181 and Ser186 mutants of bovine rhodopsin reveal only mild mutagenic perturbations of the photoproduct spectrum suggesting that dipolar, electrostatic, or steric interactions with these residues do not cause the HOOP mode frequencies and intensities. Density functional theory calculations are performed to investigate the effect of geometric distortion on the HOOP coupling. The decoupled HOOP modes can be simulated by imposing approximately 40 degrees twists in the same direction about the C(11)=C(12) and C(12)-C(13) bonds. Sequence comparison and examination of the binding site suggests that these distortions are caused by three constraints consisting of an electrostatic anchor between the protonated Schiff base and the Glu113 counterion, as well as steric interactions of the 9- and 13-methyl groups with surrounding residues. This distortion stores light energy that is used to drive the subsequent protein conformational changes that activate rhodopsin. 相似文献
35.
Yan EC Kazmi MA De S Chang BS Seibert C Marin EP Mathies RA Sakmar TP 《Biochemistry》2002,41(11):3620-3627
The second extracellular loop of rhodopsin folds back into the membrane-embedded domain of the receptor to form part of the binding pocket for the 11-cis-retinylidene chromophore. A carboxylic acid side chain from this loop, Glu181, points toward the center of the retinal polyene chain. We studied the role of Glu181 in bovine rhodopsin by characterizing a set of site-directed mutants. Sixteen of the 19 single-site mutants expressed and bound 11-cis-retinal to form pigments. The lambda(max) value of mutant pigment E181Q showed a significant spectral red shift to 508 nm only in the absence of NaCl. Other substitutions did not significantly affect the spectral features of the mutant pigments in the dark. Thus, Glu181 does not contribute significantly to spectral tuning of the ground state of rhodopsin. The most likely interpretation of these data is that Glu181 is protonated and uncharged in the dark state of rhodopsin. The Glu181 mutants displayed significantly increased reactivity toward hydroxylamine in the dark. The mutants formed metarhodopsin II-like photoproducts upon illumination but many of the photoproducts displayed shifted lambda(max) values. In addition, the metarhodopsin II-like photoproducts of the mutant pigments had significant alterations in their decay rates. The increased reactivity of the mutants to hydroxylamine supports the notion that the second extracellular loop prevents solvent access to the chromophore-binding pocket. In addition, Glu181 strongly affects the environment of the retinylidene Schiff base in the active metarhodopsin II photoproduct. 相似文献
36.
Microorganisms are associated with a variety of ancient geological materials. However, conclusive proof that these organisms
are as old as the geological material and not more recent introductions has generally been lacking. Over the years, numerous
reports of the isolation of ancient bacteria from geological materials have appeared. Most of these have suffered from the
fact that the protocol for the surface sterilization of the sample was either poorly defined, inadequate or rarely included
data to validate the overall effectiveness of the sterilization protocol. With proper sterility validation and isolation protocol,
a legitimate claim for the isolation of an ancient microbe can be made. Biochemical, physiological, or morphological data
indicate that these ancient microbes are not significantly different from modern isolates. As the role (decomposition) of
modern and ancient microbes has not changed over time, it is probably unreasonable to expect these organisms to be vastly
different. A discussion on the reasons for the homogeneity of ancient and modern microbes is presented. Journal of Industrial Microbiology & Biotechnology (2002) 28, 32–41 DOI: 10.1038/sj/jim/7000174
Received 20 May 2001/ Accepted in revised form 16 June 2001 相似文献
37.
Kinetic studies of the reduction of ferrioxamine B (Fe(Hdesf)+) by Cr(H2O)62+, V(H2O)62+, and dithionite have been performed. For Cr(H2O)62+ and V(H2O)62+, the rate is ?d[Fe(Hdesf)+]/dt = k[Fe(Hdesf)+][M2+]. For Cr(H2O)62+, k = 1.19 × 104 M?1 sec?1 at 25°C and μ = 0.4 M, and k is independent of pH from 2.6 to 3.5. For V(H2O)62+, k = 6.30 × 102 M?1 sec?1 at 25°C, μ = 1.0 M, and pH = 2.2. The rate is nearly independent of pH from 2.2 to 4.0. For Cr(H2O)62+ and V(H2O)62+, the activation parameters are ΔH≠ = 8.2 kcal mol?1, ΔS≠ ?12 eu and ΔH≠ = 1.7 kcal mol?1, ΔS≠ = ?40 eu (at pH 2.2) respectively. Reduction by Cr(H2O)62+ is inner-sphere, while reduction by V(H2O)62+ is outer-sphere. Reduction by dithionite follows the rate law ?d[Fe(Hdesf)+]/dt =kK[Fe(Hdesf)+][S2O42?] where K is the equilibrium constant for dissociation of S2O42? into SO2? radicals. The value of k at 25°C and μ = 0.5 is 2.7 × 103 M?1 sec?1 at pH 5.8, 3.5 × 103 M?1 sec?1 at pH 6.8, and 4.6 × 103 M?1 sec?1 at pH 7.8, and ΔH≠ = 6.8 kcal mol?1 and ΔS≠ = ?19 eu at pH 7.8. 相似文献
38.
Amber Farooqui Adnan Khan Ilaria Borghetto Shahana U. Kazmi Salvatore Rubino Bianca Paglietti 《PloS one》2015,10(2)
Synergistic combinations of antimicrobial agents with different mechanisms of action have been introduced as more successful strategies to combat infections involving multidrug resistant (MDR) bacteria. In this study, we investigated synergistic antimicrobial activity of Camellia sinensis and Juglans regia which are commonly used plants with different antimicrobial agents. Antimicrobial susceptibility of 350 Gram-positive and Gram-negative strains belonging to 10 different bacterial species, was tested against Camellia sinensis and Juglans regia extracts. Minimum inhibitory concentrations (MICs) were determined by agar dilution and microbroth dilution assays. Plant extracts were tested for synergistic antimicrobial activity with different antimicrobial agents by checkerboard titration, Etest/agar incorporation assays, and time kill kinetics. Extract treated and untreated bacteria were subjected to transmission electron microscopy to see the effect on bacterial cell morphology. Camellia sinensis extract showed higher antibacterial activity against MDR S. Typhi, alone and in combination with nalidixic acid, than to susceptible isolates.” We further explore anti-staphylococcal activity of Juglans regia that lead to the changes in bacterial cell morphology indicating the cell wall of Gram-positive bacteria as possible target of action. The synergistic combination of Juglans regia and oxacillin reverted oxacillin resistance of methicillin resistant Staphylococcus aureus (MRSA) strains in vitro. This study provides novel information about antimicrobial and synergistic activity of Camellia sinensis and Juglans regia against MDR pathogens 相似文献
39.
Architecture of epigenetic reprogramming following Twist1-mediated epithelial-mesenchymal transition
Gabriel G Malouf Joseph H Taube Yue Lu Tapasree Roysarkar Shoghag Panjarian Marcos RH Estecio Jaroslav Jelinek Jumpei Yamazaki Noel J-M Raynal Hai Long Tomomitsu Tahara Agata Tinnirello Priyanka Ramachandran Xiu-Ying Zhang Shoudan Liang Sendurai A Mani Jean-Pierre J Issa 《Genome biology》2013,14(12):R144
40.
Tyagi Vinay Kumar Ali Muntjeer Tawfik Ahmed Maharjan Namita Kazmi A. A. Okubo Tsutomu Harada Hideki 《Reviews in Environmental Science and Biotechnology》2021,20(2):389-418
Reviews in Environmental Science and Bio/Technology - The down-flow hanging sponge (DHS) process has been rigorously studied as a significant post-treatment of anaerobically pretreated sewage and... 相似文献