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121.
Papia Chowdhury Tirtha Pratim Adhikary Sankar Chakravorti 《Journal of luminescence》2008,128(7):1113-1120
In this paper, an interesting transformation of the emission of anionic conformer of 2-benzoyl bezimidazole in ionic and non-ionic micelles is reported. Deprotonation is hindered in cationic and non-ionic micelles owing to probe molecule's passage deep inside positive ion-rich Stern-layer in contrast with anionic micelle. The orientation of probe molecule in the two ionic micelles, as determined from the spectral properties is opposite in nature. Micellar environment shields the formation of mono- and di-cationic species at very low pH. Three decay times of the probe in different time domains were attributed to three possible anionic species and they are modified differently in ionic and neutral micelles. Quantum chemical calculations also predict the existence of three different possible anionic species. 相似文献
122.
V.K. Sinha S.K. Malik D.T. Adroja J. Elbicki S.G. Sankar W.E. Wallace 《Journal of magnetism and magnetic materials》1989,80(2-3):281-284
The DyTiFe11 - xCox (x = 0, 1, 3), HoTiFe11 - xCox (x = 0, 3) and ErTiFe11 compounds, all exhibiting the T hMn12-type structure, were studied for their ac susceptibility in the temperature range 20–300 K. The Dy- and Ho-containing compounds exhibited spin reorientation from axial to cone to planar, or from axial to cone in the temperature range 250-50 K, as expected. In this structure Dy and Ho with negative second-order Stevens' coefficients (J < 0) favor planar rare earth sublattice anisotropy, while Fe and Co sublattices favor uniaxial and planar anisotropies, respectively and would be in competition as a function of temperature. A spin-reorientation type of behavior was also observed in the ErTiFe11 compound near 50 K. This observation appears to imply that, in this compound, the higher-order crystal-field terms are important. The magnetization data revealed that in these systems the rare earth and transition metal sublattices coupled antiparallel, as is normally the case in the heavy rare-earth-transition-metal compounds. 相似文献
123.
Cloning of the Orange Light‐Producing Luciferase from Photinus scintillans—A New Proposal on how Bioluminescence Color is Determined
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Bruce R. Branchini Tara L. Southworth Danielle M. Fontaine Martha H. Murtiashaw Alex McGurk Munya H. Talukder Rakhshi Qureshi Deniz Yetil Jesse A. Sundlov Andrew M. Gulick 《Photochemistry and photobiology》2017,93(2):479-485
Unlike the enchanting yellow‐green flashes of light produced on warm summer evenings by Photinus pyralis, the most common firefly species in North America, the orange lights of Photinus scintillans are infrequently observed. These Photinus species, and likely all bioluminescent beetles, use the same substrates beetle luciferin, ATP and oxygen to produce light. It is the structure of the particular luciferase enzyme that is the key to determining the color of the emitted light. We report here the molecular cloning of the P. scintillans luc gene and the expression and characterization of the corresponding novel recombinant luciferase enzyme. A comparison of the amino acid sequence with that of the highly similar P. pyralis enzyme and subsequent mutagenesis studies revealed that the single conservative amino acid change tyrosine to phenylalanine at position 255 accounted for the entire emission color difference. Additional mutagenesis and crystallographic studies were performed on a H‐bond network, which includes the position 255 residue and five other stringently conserved beetle luciferase residues, that is proximal to the substrate/emitter binding site. The results are interpreted in the context of a speculative proposal that this network is key to the understanding of bioluminescence color determination. 相似文献
124.
Rupom Borah Eramoni Saikia Sankar Jyoti Bora Bolin Chetia 《Tetrahedron letters》2017,58(12):1211-1215
A green and facile novel procedure has been developed for the synthesis of Cu2O nanoparticles within a very short reaction time using banana pulp extract as a reducing agent. The synthesized nanoparticles are well characterized by SEM (Scanning Electron Microscope), TEM (Transmission Electron Microscope) and powder XRD (X-ray Diffraction) methods. An environmental benign and highly efficient protocol for the ipso-hydroxylation of aryl and hetero arylboronic acids using bio-fabricated Cu2O nanoparticles as a catalyst and aqueous H2O2 as an oxidant has also been developed. The main advantages of this protocol are the base free reaction condition, reusable and heterogeneous catalytic system, and short reaction time with excellent yields. 相似文献
125.
Gómez-Hortigüela L Corà F Sankar G Zicovich-Wilson CM Catlow CR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(46):13638-13645
In this work we apply state-of-the-art electronic-structure-based computational methods based on hybrid-exchange density functional theory to study the mechanism of the aerobic oxidation of hydrocarbons catalysed by Mn-doped nanoporous aluminophosphates (Mn-AlPOs). We compare our results with available experimental data. We show that the catalytic efficiency of Mn-AlPOs in oxidation reactions is intrinsically linked to 1) the Mn redox activity, in particular between 2+ and 3+ oxidation states, and 2) the coordinative insaturation of tetrahedral Mn embedded in AlPO frameworks, which facilitates the reaction by stabilising oxo-type radicals through the formation of Mn complexes. Our mechanism demonstrates the crucial role of both Mn(III) and Mn(II) in the reaction mechanism: Mn(III) sites undergo an initial reaction cycle that leads to the production of the alkyl hydroperoxide intermediate, which can only be transformed into the oxidative products (alcohol, aldehyde and acid) by Mn(II). A preactivation step is required to yield the reduced Mn(II) sites able to decompose the hydroperoxide intermediates; this step takes place through a transformation of the hydrocarbon into the corresponding peroxo-derivative, stabilised by forming a complex with Mn(III) and yielding at the same time reduced Mn(II) sites. Both species enter a subsequent propagation cycle in which Mn(II) catalyses the dissociation of the hydroperoxide that proceeds until the formation of the oxidative products by two parallel pathways, through alkoxy- or hydroxy-radical-like intermediates, whilst the Mn(III)-peroxo complex enables further production of the hydroperoxide intermediate. 相似文献
126.
Anuva Samanta Bijan Kumar Paul Sankar Jana Nikhil Guchhait 《Photochemistry and photobiology》2010,86(5):1022-1029
The photophysical properties of 5-(4-fluorophenyl)-2-hydroxypyridine (FP2HP) at different pH and its fluorescence response toward different transition metal ions have been studied by steady-state absorption and emission spectroscopy in combination with quantum chemical calculations. Although keto-enol tautomerization is observed in the excited state, the molecule is weakly fluorescent due to the presence of electron-rich nitrogen atom and relatively electron-deficient fluorine atom, which may lead to photoinduced electron transfer process. In the presence of the transition metal ions, such as Zn2+, Cd2+, Hg2+, etc., the studied molecule exhibits changes in its absorption and emission properties. The present system shows fluorescence enhancement instead of usual quenching in presence of the transition metal ions, such as Fe2+ and Cu2+. Spectral observation leads to the interpretation that this structurally simple molecule can be effectively utilized as a chelation-enhanced fluorescence-based chemosensor for the detection of transition metal ions. The experimental findings corroborate well with theoretical calculations at Hartree–Fock level using 6-31G** and lanl2dz basis sets. 相似文献
127.
Indigo is one of the oldest dyes manufactured chemically and is mostly used in textile, food, and pharmaceutical industries.
However, owing to the environmental hazards posed by the chemical production, the present scenario in the field stipulates
a biosynthesis alternative for indigo production. The present study describes an indigenously isolated naphthalene-degrading
strain Pseudomonas sp. HOB1 producing a blue pigment when indole was added in the growth medium. This blue pigment was analyzed by high-pressure
thin-layer chromatography and other spectroscopic techniques which revealed it to be the indigo dye. Pseudomonas sp. HOB1 showed ability to produce 246 mg indigo liter−1 of the medium. The K
m for the enzyme naphthalene dioxygenase which is involved in indigo formation is 0.3 mM, and V
max was as high as 50 nmol min−1 mg dry biomass−1. The bacterial indigo dye was further successfully applied for dyeing cotton fabrics. The high indigo productivity of Pseudomonas sp. HOB1 using naphthalene as growth substrate and its applicability on cotton fabrics, therefore, stems the probability
of using this culture for commercial indigo production. 相似文献
128.
Yughandhar Sreedhar Neelam Rekha Dasari P. Reddy Prasad M. Sankar Nayak 《Journal of Saudi Chemical Society》2010,14(2):149-155
A novel analytical reagent 4-(2-hydroxy phenyl ethaminodiol), benzene-1,3-diol(4-2-HPEDB-1,3,D) was synthesized for the determination of molybdenum(VI). The present paper reveals the detailed study of electroanalytical behaviour for [Mo-(4-2-HPEDB-1,3,D)] complex under optimized conditions. The peak obtained for [Mo-(4-2-HPEDB-1,3,D)] prevent the interference of foreign ions which shows the sensitivity of the proposed method. The linearity was maintained at the concentration range of 0.5–200 μg/mL at pH 4.5 with correlation factor 0.9997. The present method was successfully applied for the analysis of molybdenum(VI) in biological fluids and plant material. The results obtained from the proposed method show good agreement with reference method. 相似文献
129.
Robert Gruar Christopher James Tighe Lee M. Reilly Gopinathan Sankar Jawwad Arshad Darr 《Solid State Sciences》2010,12(9):1683-1686
Herein, we report the rapid single step hydrothermal synthesis of phase pure Bi2MoO6 (koechlinite) and Bi2Mo3O12, via a continuous hydrothermal flow synthesis (CHFS) reactor, which uses supercritical water of 375–450 °C at a pressure of 24.1 MPa as a crystallising medium. The product being obtained as highly crystalline nano-materials with high surface area. Simple variation in synthesis condition and appropriate solution stoichiometry were shown to be sufficient to select the phase of the product. The materials synthesised showed significant photcatalytic activity towards the decolourisation of methylene blue in comparison to a commercial gold standard photocatalyst. 相似文献
130.
R. D. Bhanushali Sachin S. Pathak I. C. Pius S. K. Mukerjee 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(3):647-651
Based on the Linssi database and UniSampo/Shaman software, an automated analysis platform has been setup for the analysis
of large amounts of gamma-spectra from the primary coolant monitoring systems of a CANDU reactor. Thus, a database inventory
of gaseous and volatile fission products in the primary coolant of a CANDU reactor has been established. This database is
comprised of 15,000 spectra of radioisotope analysis records. Records from the database inventory were retrieved by a specifically
designed data-mining module and subjected to further analysis. Results from the analysis were subsequently used to identify
the reactor coolant half-life of 135Xe and 133Xe, as well as the correlations of 135Xe and 88Kr activities. 相似文献