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101.
Dinesh S. Bobade Yatish R. Parauha Sanjay J. Dhoble Prabhakar B. Undre 《Luminescence》2022,37(3):500-513
The present communication is strongly focused on the investigation of synthesis, structural and luminescence properties of cerium (Ce3+)- and europium (Eu3+)-activated Zn4Al22O37 phosphors. Ce3+- and Eu3+-doped Zn4Al22O37 novel phosphors were prepared using a solution combustion synthesis route. Structural properties were studied using powder X-ray diffraction and high-resolution transverse electron microscopy. The optical properties were studied using ultraviolet–visible light spectroscopy and Fourier transform infrared spectroscopy; luminescence properties were studied using a photoluminescence (PL) technique. The crystal structure of the prepared Zn4Al22O37 host and Ce3+- and Eu3+-activated Zn4Al22O37 phosphors was investigated and was found to have a hexagonal structure. The measured PL emission spectrum of the Ce3+-doped Zn4Al22O37 phosphor showed an intense and broad emission band centred at 421 nm under a 298 nm excitation wavelength. By contrast, the Eu3+-doped Zn4Al22O37 phosphor exhibited two strong and intense emission bands at approximately 594 nm (orange) and 614 nm (red), which were monitored under 395 nm excitation. The Commission Internationale de l’Eclairage (CIE) colour coordinates of the Ce3+-doped Zn4Al22O37 were investigated and found to be x = 0.1567, y = 0.0637 (blue) at 421 nm and for Eu3+-doped Zn4Al22O37 were x = 0.6018, y = 0.3976 (orange) at 594 nm and x = 0.6779, y = 0.3219 (red) at 614 nm emission. The luminescence behaviour of the synthesized phosphors suggested that these phosphors may be used in lighting applications. 相似文献
102.
Basha SJ Naveed SA Tiwari NK Shashikumar D Muzeeb S Kumar TR Kumar NV Rao NP Srinivas N Mullangi R Srinivas NR 《Journal of chromatography. B, Analytical technologies in the biomedical and life sciences》2007,853(1-2):88-96
Simultaneous separation and quantification of ezetimibe (EZM) and its phase-I metabolite i.e., ezetimibe ketone (EZM-K) and phase-II metabolite i.e., ezetimibe glucuronide (EZM-G) in various matrices was accomplished by gradient HPLC with UV detection. The assay procedure involved deproteinization of 500 microL of either incubation or bile sample containing analytes and internal standard (IS, theophylline) with 75 microL acetonitrile containing 25% perchloric acid. An aliquot of 100 microL supernatant was injected onto a C18 column. The chromatographic separation was achieved by gradient elution consisting of 0.05 M formic acid:acetonitrile:methanol:water at a flow rate of 1.0 mL/min. The detection of analyte peaks were achieved by monitoring the eluate using an UV detector set at 250 nm. Nominal retention times of IS, EZM-G, ezetimibe ketone glucuronide (EZM-KG), EZM and EZM-K were 9.39, 24.23, 27.82, 29.04 and 30.56 min, respectively. Average extraction efficiencies of EZM, EZM-G and IS was >75-80% and for EZM-K was >50% from all the matrices tested. Limit of quantitation (LOQ) for EZM, EZM-K and EZM-G was 0.02 microg/mL. Due to the lack of availability of reference standard of EZM-KG, the recovery and LOQ aspects for this metabolite were not assessed. Overall, the method is suitable for simultaneous measurement of EZM, and its phase-I and phase-II metabolite (EZM-G) in in vitro and in vivo studies. 相似文献
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105.
Prabhakar V Capila I Raman R Srinivasan A Bosques CJ Pojasek K Wrick MA Sasisekharan R 《Biochemistry》2006,45(37):11130-11139
The chondroitinases are bacterial lyases that specifically cleave chondroitin sulfate and/or dermatan sulfate glycosaminoglycans. One of these enzymes, chondroitinase ABC I from Proteus vulgaris, has the broadest substrate specificity and has been widely used to depolymerize these glycosaminoglycans. Biochemical and structural studies to investigate the active site of chondroitinase ABC I have provided important insights into the catalytic amino acids. In this study, we demonstrate that calcium, a divalent ion, preferentially increases the activity of chondroitinase ABC I toward dermatan versus chondroitin substrates in a concentration-dependent manner. Through biochemical and biophysical investigations, we have established that chondroitinase ABC I binds calcium. Experiments using terbium, a fluorescent calcium analogue, confirm the specificity of this interaction. On the basis of theoretical structural models of the enzyme-substrate complexes, specific amino acids that could potentially play a role in calcium coordination were identified. These amino acids were investigated through site-directed mutagenesis studies and kinetic assays to identify possible mechanisms for calcium-mediated processing of the dermatan substrate in the active site of the enzyme. 相似文献
106.
R. Ranga Rao Ashok K. Tiwari P. Prabhakar Reddy K. Suresh Babu Amtul Z. Ali K. Madhusudana J. Madhusudana Rao 《Bioorganic & medicinal chemistry》2009,17(14):5170-5175
A bioassay-guided fractionation and chemical examination of antihyperglycemic root extract of Derris indica resulted in isolation and characterization of two new furanoflavanoids (1, 2) along with thirteen known compounds (3–15). Their structures were determined on the basis of extensive spectroscopic (IR, MS, 1D and 2D NMR) data analysis and by comparison with the literature data. All the compounds were tested in vitro for intestinal α-glucosidase inhibitory and DPPH radical activity. New compounds (1, 2) displayed moderate intestinal α-glucosidase inhibitory as well as free radical scavenging activity. Other compounds also displayed varying degrees of moderate intestinal α-glucosidase inhibitory activity. Pongamol (6) displayed potent intestinal α-glucosidase inhibition. 相似文献
107.
P. Prabhakar Reddy Ashok K. Tiwari R. Ranga Rao K. Madhusudhana V. Rama Subba Rao Amtul Z. Ali K. Suresh Babu J. Madhusudana Rao 《Bioorganic & medicinal chemistry letters》2009,19(9):2562-2565
Phytochemical investigation of antihyperglycemic extract of rhizomes of Hedychium spicatum led to the isolation of two new labdane type diterpenes 2, 3 along with seven known compounds (1, 4–9). Their structures were established on the basis of NMR (1D and 2D) and mass spectroscopic analysis. The new compound 2 displayed strong intestinal α-glucosidase inhibitory activity. Other compounds also displayed varying degree of intestinal α-glucosidase inhibitory potential. 相似文献
108.
Karen J. Meaburn Prabhakar R. Gudla Sameena Khan Stephen J. Lockett Tom Misteli 《The Journal of cell biology》2009,187(6):801-812
Genomes are nonrandomly organized within the three-dimensional space of the cell nucleus. Here, we have identified several genes whose nuclear positions are altered in human invasive breast cancer compared with normal breast tissue. The changes in positioning are gene specific and are not a reflection of genomic instability within the cancer tissue. Repositioning events are specific to cancer and do not generally occur in noncancerous breast disease. Moreover, we show that the spatial positions of genes are highly consistent between individuals. Our data indicate that cancer cells have disease-specific gene distributions. These interphase gene positioning patterns may be used to identify cancer tissues. 相似文献
109.
Prabhakar V Capila I Soundararajan V Raman R Sasisekharan R 《The Journal of biological chemistry》2009,284(2):974-982
Chondroitin lyases (or chondroitinases) are a family of enzymes that depolymerize chondroitin sulfate (CS) and dermatan sulfate (DS) galactosaminoglycans, which have gained prominence as important players in central nervous system biology. Two distinct chondroitinase ABC enzymes, cABCI and cABCII, were identified in Proteus vulgaris. Recently, cABCI was cloned, recombinantly expressed, and extensively characterized structurally and biochemically. This study focuses on recombinant expression, purification, biochemical characterization, and understanding the structure-function relationship of cABCII. The biochemical parameters for optimal activity and kinetic parameters associated with processing of various CS and DS substrates were determined. The profile of products formed by action of cABCII on different substrates was compared with product profile of cABCI. A homology-based structural model of cABCII and its complexes with CS oligosaccharides was constructed. This structural model provided molecular insights into the experimentally observed differences in the product profile of cABCII as compared with that of cABCI. The critical active site residues involved in the catalytic activity of cABCII identified based on the structural model were validated using site-directed mutagenesis and kinetic characterization of the mutants. The development of such a contaminant-free cABCII enzyme provides additional tools to decode the biologically important structure-function relationship of CS and DS galactosaminoglycans and offers novel therapeutic strategies for recovery after central nervous system injury. 相似文献
110.
Prabhakar KR Veerapur VP Bansal P Vipan KP Reddy KM Barik A Reddy BK Reddanna P Priyadarsini KI Unnikrishnan MK 《Bioorganic & medicinal chemistry》2006,14(21):7113-7120
Treatment of phenols with ninhydrin in acidic medium afforded 2-hydroxy-2-(ortho-hydroxy-phenyl/naphthyl)-1,3-dioxoindanes, which being unstable were isolated in their hemiketal forms. These synthesized compounds were subjected to TLC screening for radical scavenging and in vitro lipoxgenase and cycloxygenase enzyme inhibition assays. The best compound was identified and studied in detail for steady-state and time-resolved free radical kinetics, viz., DPPH, ABTS(-), *OH and rate constants for these reactions were evaluated. The best compound was also subjected to in vivo anti-inflammatory and analgesic activities in which the compound showed good promise for further structural optimization. 相似文献