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S. Md. AKBAR,S. K. JAYALAKSHMI,H. C. SHARMA,K. SREERAMULU 한국곤충학회 2011 Entomological Research Vol.41 No.6
Dihydrolipoamide dehydrogenase (DHLDH) was isolated from the mitochondria of Helicoverpa armigera, a destructive pest which has developed resistance to commonly used insecticides. The flavoenzyme was purified 17.98-fold to homogeneity with an overall yield of 10.53% by employing ammonium sulfate precipitation, hydroxylapatite chromatography and CM-Sephadex chromatography. The purified enzyme exhibited the specific activity of 18.7 U/mg and was characterized as a dimer with a subunit mass of 66 kDa. The enzyme showed specificity for nicotinamide adenine dinucleotide – hydrogen (NADH) and lipoamide, as substrates, with Michaelis-Menten constants (K_m) of 0.083 mmol/L and 0.4 mmol/L, respectively. The reduction reaction of lipoamide by the enzyme could be explained by ping-pong mechanism. The spectra of DHLDH showed the maximum absorbance at 420 nm, 455 nm and 475 nm. The enzyme activity was strongly inhibited by mercurial and arsenical compounds. The N-terminal sequence of Ha-DHLDH showed homology with those of mammalian and arthropod DHLDH. Since H. armigera has developed high levels of resistance to commonly used insecticides, biochemical properties of the metabolic enzymes such as DHLDH, could be helpful to develop insecticidal molecules for the control of H. armigera, with a different mode of action.
Sharma, A.,Varshney, M.,Chae, K.H.,Shin, H.J.,Won, S.O. Elsevier 2016 Current Applied Physics Vol.16 No.10
<P>We investigated local electronic/atomic structure properties by using X-ray absorption spectroscopy and demonstrated the photocatalyst application of Zr1-xCuxO2 (0 <= x <= 0.2) samples. X ray diffraction (XRD) results revealed the amorphous nature of the samples; however, transmission electron microscopy (TEM) depicted the formation of < 2 nm sized particles in all of the samples. Local electronic structure was investigated by X-ray absorption near edge structure (XANES) at O K-edge, Zr K-edge and Cu K-edge. The O K-edge XANES suggested strong hybridization of s-p-d orbitals upon Cu doping. The Cu K-edge XANES confirmed +1 valence state of Cu (Cu+1) in all of the Cu doped ZrO2 samples. Extended X-ray absorption fine structure (EXAFS) analysis at the Zr K-edge nullifies the formation of trivial phases and confirms the local monoclinic structure in all of the samples. Photocatalyst properties of the samples were investigated by monitoring the net degradation in the methyl orange dye aqueous solution under the UV light irradiation. The Cu doped ZrO2 samples exhibited superior photo-catalyst properties over the undoped ZrO2. (C) 2016 Elsevier B.V. All rights reserved.</P>
Sankar, S.,Sharma, S.K.,Kaur, N.,Lee, B.,Kim, D.Y.,Lee, S.,Jung, H. Ceramurgica ; Elsevier Science Ltd 2016 CERAMICS INTERNATIONAL Vol.42 No.4
An inexpensive chemical method was used to synthesize biogenic mesoporous silica (m-SiO<SUB>2</SUB>) from rice husk ash (RHA). A comparative study was carried out to produce silica nanoparticles (S-SiO<SUB>2</SUB>, R-SiO<SUB>2</SUB>, and B-SiO<SUB>2</SUB>) from three type of rice husk ashes (sticky, red, and brown). The microstructure of m-SiO<SUB>2</SUB> was dependent on the geographical provenance and the types of RHA. An analysis of the SEM and TEM micrographs reveals that the S-SiO<SUB>2</SUB> nanoparticles had a clustered spherical shape, while R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanoparticles were found to be purely spherical. The average crystallite size of S-SiO<SUB>2,</SUB> R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanoparticles evaluated from the TEM measurements were observed to be 50, 20 and 10nm, respectively. The XRD pattern of silica nanopowders had an absence of sharp peaks that confirmed the amorphous nature of the material. The Fourier transform infrared (FTIR) spectra of silica nanoparticles showed the symmetric Si-O and O-Si-O stretching bond vibrations at 462, 1088, and 1098cm<SUP>-1</SUP>. The surface area of S-SiO<SUB>2,</SUB> R-SiO<SUB>2</SUB> and B-SiO<SUB>2</SUB> nanopowders was measured to be 7.5513, 201.45, and 247.18m<SUP>2</SUP>g<SUP>-1</SUP>, respectively. The surface area of uniformly-distributed spherical nanoparticles of B-SiO<SUB>2</SUB> was observed the highest, which can be applied for the application of energy storage and drug delivery systems.
Jo, H.,Park, J.,Mishra, N.K.,Jeon, M.,Sharma, S.,Oh, H.,Lee, S.Y.,Jung, Y.H.,Kim, I.S. Pergamon Press 2017 Tetrahedron Vol.73 No.13
The ruthenium(II)-catalyzed site-selective acylation of indolinic C-H bonds with ethyl glyoxalate is described. A cationic ruthenium catalyst in the presence of copper(II) acetate was found to be an optimal catalytic system for the construction of C7-indolinyl ketoesters. In this process, C-H addition reaction first takes place, and subsequent oxidation of alcohol intermediates occur in-situ. The formed C7-functionalized indolines can be a crucial array towards the construction of novel bioactive molecules.
Influence of growth temperature and post-annealing on an n-ZnO/p-GaN heterojunction diode
Sharma, S.K.,Heo, S.,Lee, B.,Lee, H.,Kim, C.,Kim, D.Y. Elsevier 2014 CURRENT APPLIED PHYSICS Vol.14 No.12
We report on an n-ZnO/p-GaN heterojunction diode fabricated from zinc oxide (ZnO) films at various growth temperatures (450, 500, 550, and 600 <SUP>o</SUP>C) by RF sputtering. The films were subsequently annealed at 700 <SUP>o</SUP>C in N<SUB>2</SUB> ambient. To investigate the influence of the growth temperature of n-ZnO films, the microstructural, optical, and electrical properties were measured using scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), and Hall measurements. The XRD pattern showed the preferred orientation along the c-axis (002) regardless of growth temperature. The PL spectra showed a dominant sharp near-band-edge (NBE) emission. Current-voltage (I-V) curves showed excellent rectification behavior. The turn-on voltage of the diode was observed to be 3.2 V for the films produced at 500 <SUP>o</SUP>C. The ideality factor of ZnO film was observed to be 1.37, which showed the best performance of the diode.
Sharma, A.,Varshney, M.,Shin, H.J.,Chae, K.H.,Won, S.O. Elsevier 2016 CURRENT APPLIED PHYSICS Vol.16 No.10
<P>Tin oxide nanostructures are nontoxic in nature and biocompatible. However, they exhibit weak emission characteristics that limit their applications in cellular and biology fields. Therefore, it is important to enhance luminescence properties in this oxide and establish a relationship between the local electronic structure and emission characteristics. In this report, we demonstrate significant advancement in the photoluminescence (PL) properties in the Eu incorporated SnO2-SnO nanocomposites. Eu: SnO2-SnO nanocomposites were synthesized by chemical precipitation method. X-ray diffraction (XRD), X-ray absorption near edge structure (XANES) and PL measurements were performed to investigate the structural, electronic structure and emission properties of the samples. Eu3+ ions, as confirmed by the Eu M-5,M-4-edge XANES studies, lead to defect formation and local electronic structural perturbation in the nanocomposites. The O K-edge and Sn M-5,M-4-edge XANES studies confirm a net decrease in the hybridization of O 2p and Sn 5s/5p states and formation of Sn defects, upon Eu doping. Significant enhancement in the Eu3+ related interband transitions (D-5(0)-F-7(J); J = 0,1,2,3,4) is achieved upon increasing the Eu concentrations, indicating synthesis of emission characteristic rich SnO2-SnO nanocomposites. (C) 2016 Elsevier B.V. All rights reserved.</P>
Salen decorated nanostructured ZnO chemosensor for the detection of mercuric ions (Hg<sup>2+</sup>)
Sharma, S.K.,Kaur, N.,Singh, J.,Singh, A.,Raj, P.,Sankar, S.,Kim, D.Y.,Singh, N.,Kaur, N.,Singh, H. Elsevier Sequoia 2016 Sensors and actuators. B Chemical Vol.232 No.-
Self-assembled ZnO nanoparticles, nanodumbbells and nanorod/nanowire flowers were synthesized by the hydrothermal precipitation method, and tested them for the detection of mercuric ions (Hg<SUP>2+</SUP>) as the chemosensor. Various techniques like X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM) and photoluminescence (PL) were employed for the characterization of nanostructured ZnO powder. The surface of nanostructured ZnO was decorated with salen prepared from reported procedure. The binding ability of different nanostructured ZnO complexes with salen was tested by screening them with various metal ion solutions. The prepared solution of various ZnO complexes showed the selective affinity for mercuric ions, without having any interference from other potential interferent metal ions. The prepared complexes had a variable response and the selectivity for mercury ions, having the lowest detection limits of 20nM (nanoparticle), 18nM (nanodumbbell), 35nM (nanorod flowers) and 10nM (nanowire flowers), respectively. The detection limit/range of prepared complexes was varied with respect to the microstructures: (i) nanoparticles showed a larger dynamic range as they had more binding sites for Hg<SUP>2+</SUP> owing to more binding sites for salen, and (ii) the nanowire flowers detected the better detection limit due to its cluster nature.
3-Naphthylindoles as new promising candidate antioxidant, antibacterial, and antibiofilm agents
Sharma, K.,Baral, E. R.,Akhtar, M. S.,Lee, Y. R.,Kim, S. H.,Wee, Y. J. Springer Science + Business Media 2017 Research on chemical intermediates Vol.43 No.4
<P>Indole derivatives have attracted significant attention in organic synthesis and bioactivity research owing to their substantial biological activity. In the present study, several 3-naphthylindole analogues were synthesized by direct arylation of 1-diazonaphthalene-2-(1H)-ones by rhodium(II)-catalyzed cross-coupling reaction and their antioxidant and antibacterial properties evaluated. Among the analogues tested, compound 3m displayed the highest antioxidant activity [as evaluated by ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) tests], whereas compound 3c exhibited the lowest activity. The compounds were also screened against biofilm-forming bacterial species (Gram-negative Escherichia coli and Pseudomonas aeruginosa as well as Gram-positive Staphylococcus aureus and Bacillus cereus). Compounds 3b, i, j, p displayed potent antibacterial activity against E. coli. Similarly, compound 3p exhibited activity superior to quercetin (4.2 mu g/mL) by completely inhibiting biofilm formation by E. coli. Moreover, the half-maximal inhibitory concentration (IC50) values of compounds 3e, j against B. cereus were comparable to that of standard quercetin.</P>