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41.
Hybridization of PNA to structured DNA targets: quadruplex invasion and the overhang effect 总被引:4,自引:0,他引:4
Peptide nucleic acid (PNA) probes have been synthesized and targeted to quadruplex DNA. UV-vis and CD spectroscopy reveal that the quadruplex structure of the thrombin binding aptamer (TBA) is disrupted at 37 degrees C by a short PNA probe. The corresponding DNA probe fails to bind to the stable secondary structure at this temperature. Thermal denaturation experiments indicate surprisingly high thermal and thermodynamic stabilities for the PNA-TBA hybrid. Our results point to the nonbonded nucleobase overhangs on the DNA as being responsible for this stability. This "overhang effect" is found for two different PNA-DNA sequences and a variety of different overhang lengths and sequences. The stabilization offered by the overhangs assists the PNA in overcoming the stable secondary structure of the DNA target, an effect which may be significant in the targeting of biological nucleic acids, which will always be much longer than the PNA probe. The ability of PNA to invade a structured DNA target expands its potential utility as an antigene agent or hybridization probe. 相似文献
42.
ZnS nanoparticles of diameters of 3–4 nm were self-assembled to form dense nanospheres of sizes 100 nm by a colloidal precipitation method using PVP as the stabilizing agent. Studies indicated that the ZnS nanoparticles maintained their individual properties inside the nanospheres. Optical absorption spectra of the samples demonstrated the effect of quantum confinement in the ZnS nanocrystals. Room temperature photoluminescence measurements showed a sharp UV emission at 370 nm, attributed to sulfur vacancies. 相似文献
43.
C. B. Vijaya Vittala Sunirmal Ray S. Chaterjee T. Dharmavir Singh Kaushik Datta 《实验传热》2013,26(4):221-228
The heat transfer coefficient for condensation of steam has been determined experimentally for a cyclone surface. Ambient air is used as the coolant and the outer surface is maintained in a free-convection condition. A twofold increase in heat transfer coefficient is observed over a cyclone surface in comparison with a vertical tube. 相似文献
44.
Sreemanta Mitra Amrita Mandal Anindya Datta Sourish Banerjee Dipankar Chakravorty 《Journal of magnetism and magnetic materials》2012
Nanosheets of nickel with thickness equal to 0.6 nm have been grown within the interlayer spaces of Na-4 mica. The sheets are made up of percolative clusters of nanodisks. Magnetization characteristics indicate a superparamagnetic behavior with a blocking temperature of 428 K. The magnetic anisotropy constant as extracted from the coercivity data has been found to be higher than that of bulk nickel by two orders of magnitude. This is ascribed to a large aspect ratio of the nickel nanophase. The Bloch exponent is also found to be considerably different from that of bulk nickel because of a size effect. The Bloch equation is still found to be valid for the two dimensional structures. 相似文献
45.
Jinesh M. Kuthanapillil A. Nijamudheen Nayana Joseph Praveen Prakash E. Suresh Ayan Datta K.V. Radhakrishnan 《Tetrahedron》2013
A detailed investigation on the effect of solvent polarity, temperature, and microwave irradiation on periselectivity in cycloaddition reactions of pentafulvenes with 3-oxidopyrylium betaine is described. The base catalyzed generation of 3-oxidopyrylium betaine in CHCl3 resulted in the exclusive formation of [6+3] adducts. With increase in solvent polarity and temperature, mixtures of [6+3] and [3+2] adducts were formed, where as under microwave irradiation, [3+2] adducts were formed exclusively. The experimental results have been rationalized on the basis of theoretical calculations. 相似文献
46.
Papia Datta Dibakar Sardar Uttam Panda Ajanta Halder Nabin Baran Manik Chun‐Jung Chen Chittaranjan Sinha 《应用有机金属化学》2016,30(5):323-334
Os(II) hydridocarbonyl complexes of coumarinyl azoimidazoles, [Osh(CO)(PPh3)2(CZ‐4R‐R′)]0/+ ( 3 , 4 ) (CZ‐R‐H = 2‐(coumarinyl‐6‐azo)‐4‐substituted imidazole or 1‐alkyl‐2‐(coumarinyl‐6‐azo)‐4‐substituted imidazole), were characterized from spectroscopic data and the single‐crystal X‐ray data for one of the complexes, [Osh(CO)(PPh3)2(CZ‐4‐Ph)] ( 3c ) (CZ‐4‐Ph = 2‐(coumarinyl‐6‐azo)‐4‐phenylimidazolate), confirmed the structure. The complexes show higher emission (quantum yield ? = 0.0163–0.16) and longer lifetime (τ = 1.4–10.3 ns) than free ligands (? = 0.0012–0.0185 and τ = 0.685–1.306 ns). Cyclic voltammetry shows quasi‐reversible metal oxidation at 0.67–0.94 V for [Os(III)/Os(II)] and 1.21–1.36 V for [Os(IV)/Os(III)] and subsequent azo reductions (?0.68 to ?0.95 V for [? N?N? ]/[? N N? ]? and irreversible < ?1.2 V for [? N N? ]?/[? N? N? ]2?) of the chelated coumarinyl azoimidazole. The complexes are photostable and show better photovoltaic power conversion efficiency than free ligands. Also, the complexes were used as catalysts for the oxidation of primary/secondary alcohols to aldehydes/ketones using oxidizing agents like N‐methylmorpholine N‐oxide, t‐BuOOH and H2O2. Density functional theory computation was carried out from the optimized structures and the data obtained were used to interpret the electronic and photovoltaic properties. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
47.
“Grafting through” polymerization represents copolymerization of free monomers in solution and polymerizable units bound to a substrate. Free polymer chains are formed initially in solution and can incorporate the surface-bound monomers, and thereby, get covalently bonded to the surface during the polymerization process. As more growing chains attach to the surface-bound monomers, an immobilized polymer layer is formed on the surface. We use a combination of computer simulation and experiments to comprehend this process for monomers bound to a flat impenetrable substrate. We concentrate specifically on addressing the effect of spatial density of the surface-bound monomers on the formation of the surface-attached polymers. We employ a lattice-based Monte Carlo model utilizing the bond fluctuation model scheme to provide molecular-level insight into the grafting process. For experimental validation, we create gradients of density of bound methacrylate units on flat silicon wafers using organosilane chemistry and carry out “grafting through” free radical polymerization initiated in bulk. We report that the proximity of the surface-bound polymerizable units promotes the “grafting through” process but prevents more free growing chains to “graft through'' the polymerizable units. The “grafting through” process is self-limiting in nature and does not affect the overall density of the surface-bound polymer layer, except in case of the highest theoretical packing density of surface-bound monomers. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 263–274 相似文献
48.
Amitava Datta 《Pramana》2017,89(4):54
The searches for supersymmetry at the Large Hadron Collider (LHC) have so far yielded only null results and have considerably tightened the bounds on the sparticle masses. This has generated some skepticism in the literature regarding the ‘naturalness of SUSY’ which qualitatively requires some sparticles to be relatively light. Re-examining some of the bounds from LHC searches, it is argued with specific examples that the above skepticism is a red herring because (i) a quantitative and universally accepted definition of ‘naturalness’ is not available and (ii) even if some conventional definitions of naturalness is accepted at their face values, the alleged tension with the apparently stringent LHC bounds wither away once the strong assumptions, by no means compelling, underlying such bounds are relaxed. 相似文献
49.
Energy density, magnetomechanical coupling factor and a dimensionless sensing gage factor of 〈1 0 0〉 oriented single crystal iron-gallium alloys with 16, 17.5, 19, 24.7 and 29 at% gallium were studied as functions of stress and magnetic field. To estimate these quantities, the samples were characterized under different quasi-static stress and magnetic field conditions. The experimental behavior was modeled using an energy-based non-linear approach. Both the experimental data and the model simulations were used to calculate material parameters such as magnetic permeability, piezo-magnetic strain coefficient (d33), inverse piezo-magnetic coefficient (stress sensitivity, d*33) and Young's modulus in the material. These quantities were used to obtain energy density, magnetomechanical coupling factor and sensing gage factor as functions of magnetomechanical conditions. Maximum energy density of around 3 kJ/m3, magnetomechanical coupling factor higher than 0.75 and sensing gage factor on the order of 103 were calculated. 相似文献
50.
Orientational order parameter S is evaluated in the nematic phase of six liquid crystal compounds, N-(p-n-propyl benzylidene)-p-n-alkoxy anilines, 3.Om and N-(p-n-propyloxy benzylidene)-p-n-alkoxy anilines, 3O.Om compounds with m = 6, 7 and 8, using different methods. The techniques employed are S from birefringence δn, Haller's approximation from (1?T/Tc) β, effective geometry parameter αg and Vuks’ scaling factor SC. The values of S obtained using the above methods are compared with one another and with the results on a number of liquid crystals; the liquid crystals favor isotropic Vuks’ method. 相似文献