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排序方式: 共有116条查询结果,搜索用时 15 毫秒
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23.
Madhusudana Pulaganti Babajan Banaganapalli Chaitanya Mulakayala Suresh Kumar Chitta Anuradha C. M. 《Applied biochemistry and biotechnology》2014,172(3):1407-1432
Menaquinone is a lipid-soluble naphthoquinone that is essential for various pivotal functions of bacteria. Naphthoquinone is synthesized from chorismate of the shikimate pathway in microorganisms. Due to its absence in humans and animals, menaquinone biosynthesis has been an attractive target for development of antibiotics against a number of important microbial pathogens, such as Mycobacterium tuberculosis (Mtb). In shikimate pathway, O-succinylbenzoate synthase (OSBS) plays a major role and is one of the major potential drug targets. For Mtb-OSBS, a systematic study was conducted to get an insight about Mtb-OSBS enzyme and the corresponding inhibitors using in silico methods. The 3-D model of Mtb-OSBS was built using structure coordinates of Thermobifida fusca. O-succinylbenzoate synthase, the model, was further refined. The active site amino acids have been identified by comparing the template sequence with the Mtb-OSBS sequence. We identified that Lys108, Asn140, Asp138, Lys110, Glu189, Ser236, Asp188, Arg27, Tyr52, and Ser237 are highly conserved, and these may play a vital role as active residues, similar to that in template protein. As per the competitive binding of substrate (2-succinyl-6-hydroxy-2,4-cyclohexadiene-1-carboxylate (SHCHC)), we screened the SHCHC through AutoDock 4.0. The SHCHC molecule was further modified structurally and optimized through PRODRG server. Docking of the 12 lead molecules for best interactions with Mtb-OSBS has given an insight that all the lead molecules have shown interactions with active site amino acids of Mtb-OSBS. MD simulation analysis report has shown the stable conformation annotations of Mtb-OSBS. These hypothetical studies create another way to develop more potential drugs against the deadly mycobacterium. 相似文献
24.
A rapid and practical green route for the N-formylation of amines with formic acid using Amberlite IR-120 as a catalyst is described. This method provides an efficient and much improved modification over the reported methods in terms of yield, reaction time, and work-up procedure. A wide variety of substituents is tolerated, which is not the case for existing procedures. 相似文献
25.
A new germacrane derivative, care none (1) was isolated from the stems of a well-known medicinal plant, Carissa spinarum L. together with a new ester, 3'-(4'-methoxyphenyl)-3-oxo-ropionyl hexadecanoate (2). Their structures were established using 1D, 2D NMR spectroscopic and synthetic methods. The chloroform extract of the plant displayed strong antioxidant (DPPH) activity. Several other known compounds were also isolated for the first time from this active extract. The antioxidant activity of major lignans was studied. 相似文献
26.
We describe a chiral axial next nearest neighbour xy-model to account for the various subphases exhibited by antiferroelectric liquid crystals made of chiral rod-like molecules.
The assumed form of the interlayer interactions is based on physical processes which are discussed. Using a discrete model,
the predicted sequence of transitions is SmA-SmC-SmC-FIH-FII-FIL-SmC
*
A, where FI stands for a ferriphase, as seen in many compounds. The ferri and SmC phases are characterized by relatively large angles between the c-vectors of successive layers and occur only when the compounds have high optical purity. The calculated field induced structures
exhibit a plateau of the apparent tilt angle at , where is the tilt angle of the molecules in the ferriphase. The conoscopic figures in the presence of a field and ellipsometric
parameters in the absence of a field have also been generated, which agree extremely well with the experimental results. Recent
anomalous X-ray scattering studies prove the xy-character of the configurations, though the commensurate structures that are found in the ferriphase require an extension
of the model to include lock-in terms.
Received 23 August 1999 相似文献
27.
G. Basappa N.V. Madhusudana 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(2):179-187
We present experimental studies on the effect of strong electric fields on the nematogen p-cyanophenyl p-n-heptyl benzoate
which has the strongly polar cyano end group and a large positive dielectric anisotropy. We use a local temperature measurement
to take into account heating effects and an electrical impedance analysis to determine both the dielectric constant () and the resistance (R) of the sample. We also measure the higher harmonic responses of the medium. The new results obtained in this study are: (i)
a detailed temperature dependence of the terms which describe (a) the quenching of macroscopic thermal fluctuations of the
nematic director and (b) the enhancement of the orientational order parameter due to Kerr effect, (ii) clear evidence for
the critical divergence of susceptibility as reflected in the third harmonic signal, (iii) an unusual enhancement of the conductivity
which shows a large peak just below the critical point , (iv) a significant peak in the second harmonic signal at and (v) evidence for a field induced nematic-nematic transition well inside the nematic range. We argue that the results
(iii)-(v) indicate the presence of polar short range order in the medium and hence support a molecular model in which such an order has been proposed.
Received: 15 July 1997 / Received in final form: 24 September 1997 / Accepted: 29 October 1997 相似文献
28.
We predict the existence of a new defect-lattice phase near the nematic-smectic-C(NC) transition. This tilt-analogue of the
blue phase is a lattice of double-tilt cylinders which are disclination lines in the smectic layer normal as well as the c-field.
We discuss the structure and stability of the cone phase. We suggest that many ‘nematics’ exhibiting short range layering
and tilt order may in fact be in the molten cone phase, which is a line liquid. 相似文献
29.
Eppakayala Sreedhar R. Sateesh Chandra Kumar G. Venkateswar Reddy A. Robinson K. Suresh Babu J. Madhusudana Rao P.V. Srinivas 《Tetrahedron: Asymmetry》2009,20(4):440-448
A concise total synthesis of neohelmanticins A–D has been accomplished in 15 steps starting from commercially available gallic acid. Swern oxidation conditions, a Grignard reaction, Sharpless kinetic resolution, and regioselective ring opening of an epoxide with lithium aluminum hydride (LAH) are the key features to install the basic core, dihydroxy phenyl propane 2. One hydroxyl group of this core was esterified with tiglic acid followed by the oxidation and esterification with corresponding acids to yield neohelmanticins A–D. 相似文献
30.
Mallipattu Sreedhar Tukiakula Madhusudana Reddy Kami Reddy Sirisha Srinivasulu Reddy Jayarama Reddy 《Analytical sciences》2003,19(4):511-516
A sensitive adsorptive stripping voltammetric method for the determination of dinitrophenolic herbicides, dinoseb (DSB) and dinoterb (DTB) at a bare carbon paste electrode (CPE) and a clay modified carbon paste electrode (CMCPE) was developed. A systematic study of various experimental conditions, such as the pH, accumulation variables and composition of a modifier on the adsorptive stripping response, were examined by using differential pulse voltammetry. A significant improvement was observed in the sensitivity by using the present method with CMCPE. When CMCPE was used, a linear response was obtained over the concentration range 2 x 10(-10) to 3 x 10(-7) M and 6 x 10(-10) to 6 x 10(-7) M with lower detection limits of 1 x 10(-10) M and 5.4 x 10(-10) M for dinoseb and dinoterb, respectively, at an accumulation time of 100 s. The interference from other herbicides and ions on the stripping signals of both compounds was also evaluated. The described method was applied to estimate of the dinoseb and dinoterb in environmental samples. 相似文献