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101.
S Mogurampelly S Panigrahi D Bhattacharyya AK Sood PK Maiti 《The Journal of chemical physics》2012,137(5):054903
Using all atom molecular dynamics simulations, we report spontaneous unzipping and strong binding of small interfering RNA (siRNA) on graphene. Our dispersion corrected density functional theory based calculations suggest that nucleosides of RNA have stronger attractive interactions with graphene as compared to DNA residues. These stronger interactions force the double stranded siRNA to spontaneously unzip and bind to the graphene surface. Unzipping always nucleates at one end of the siRNA and propagates to the other end after few base-pairs get unzipped. While both the ends get unzipped, the middle part remains in double stranded form because of torsional constraint. Unzipping probability distributions fitted to single exponential function give unzipping time (τ) of the order of few nanoseconds which decrease exponentially with temperature. From the temperature variation of unzipping time we estimate the energy barrier to unzipping. 相似文献
102.
Sumit Kumar 《Journal of heterocyclic chemistry》2019,56(4):1168-1230
Cross‐coupling reactions, namely, the Suzuki–Miyaura, Heck, Sonogashira, Hiyama, Negishi, Kumada, and Hartwig–Buchwald, are the most powerful approaches in the formation of C–C, C–N, C–O, and C–S bonds for the complex organic scaffolds in drugs, natural products, organic materials, and fine chemicals. The nitrogen‐based ligands have upper hands in these reactions because they are air stable, inexpensive, and easier to handle than the phosphorous counterparts. In this perspective, Schiff bases and N‐heterocyclic carbenes have been explored extensively in terms of novel design and preparation as ligands in the coupling reactions. Facile recovery and reusability of these ligands make them eco‐friendly and economical. A comprehensive outline on the progress in Schiff bases–metal complexes and NHC–metal complexes that mediated cross‐coupling reactions with recent examples highlighted is reported (160 references). 相似文献
103.
Dalal Anuj Nehra Kapeesha Hooda Anjli Singh Sitender Singh Devender Kumar Sumit 《Journal of fluorescence》2022,32(3):1019-1029
Journal of Fluorescence - This article presents four ternary terbium complexes based on fluorinated 2-thenoyltrifluoroacetone (TTFA) and N donor bidentate neutral ligands. The prepared complexes... 相似文献
104.
The γ- and conversion electron spectra following131Ba ε-decay are investigated, using HPGe detector and mini-orange electron spectrometer. Attention is particularly focussed
on identifying weak transitions associated with low energy high spin levels in131Cs level scheme earlier inferred in reaction studies but not yet observed in131Ba decay. Our experiment identifies 15 new gammas and 6 new conversion lines in this decay. Internal conversion coefficients
and multipolarities of several transitions are determined. Five new levels (3 with Iπ = 7/2+ and one each with Iπ 9/2+ and 11/2−) are introduced in the131Cs level scheme based on our observations taken together with the results from reaction studies. Spin-parity assignments to
a few other levels are also suggested 相似文献
105.
The flow of various liquids and gases over single-walled carbon nanotube bundles induces an electrical signal (voltage/current)
in the sample along the direction of the flow. The electrical response generated by the flow of liquids is found to be logarithmic
in the flow speed over a wide range. In contrast, voltage generated by the flow of gas is quadratically dependent on the gas
flow velocity. It was found that the underlying physics for the generation of electrical signals by liquids and gases are
different. For the liquid, the Coulombic interaction between the ions in the liquid and the charge carriers in the nanotube
plays a key role while electrical signal generation due to gas flow is due to an interplay of Bernoulli’s principle and Seebeck
effect. Unlike the liquid case which is specific to the nanotubes, the gas flow effect can be seen for a variety of solids
ranging from single and multi-walled carbon nanotubes, graphite and doped semiconductors. 相似文献
106.
Unequal connections 总被引:2,自引:0,他引:2
Empirical work suggests that social and economic networks are characterized by an unequal distribution of connections across individuals. This paper explores the circumstances under which networks will or will not exhibit inequality. Two specific models of network formation are explored. The first is a playing the field game in which the aggregate payoffs of an individual depend only on the number of his links and the aggregate number of links of the rest of the population. The second is a local spillovers game in which the aggregate payoffs of an individual depend on the distribution of links of all players and the identity of neighbors. For both class of games we develop results on existence and characterize equilibrium networks under different combinations of externalities/spillovers. We also examine conditions under which having more connections implies a higher payoff. 相似文献
107.
Residual interaction calculations have been made for predicting the sign and the magnitude of the odd-even shifts observed
in the rotational levels of theK=0 bands in the doubly-odd rare earth nuclei. It is shown that, contrary to the conclusions reached in earlier studies, the
same zero-range spin-dependent residual interaction can reproduce the odd-even shifts as well as the GM splitting energies.
This has been made possible with the inclusion of the phase factors for the total intrinsic spin and the total parity of the
two-quasi-particle states in the Newby matrix elements. Predictions are made for the odd-even shifts for otherK=0 bands arising from several configurations not confirmed or observed so far. 相似文献
108.
M. S. Hundal Geeta Sood Parveen Kapoor S. S. Tandon 《Journal of chemical crystallography》1988,18(5):601-607
The title compound C18H18N2O2S is monoclinic with unit-cell dimensionsa=8.849(10),b=9.185(11),c=20.257(9) Å,=109.28(10)°. The space group isP21/c, withZ=4. Data were measured by photographic methods. The structure was solved by direct methods. A full-matrix least-squares refinement converged toR=0.10. All atoms except sulfur were assigned individual isotropic thermal parameters. The conformation of the thiadiazepine ring system is distorted boat shaped, as indicated by torsion angle studies. 相似文献
109.
Deepika Kathuria Sumit S. Chourasiya Sanjay K. Mandal Asit K. Chakraborti Uwe Beifuss Prasad V. Bharatam 《Tetrahedron》2018,74(23):2857-2864
Treatment of 1,3-diaryl-propene-2-one with aminoguanidine under acidic conditions for a short reaction period (1?h) delivers - in accordance with a literature report - the corresponding guanylhydrazones. However, when the reaction time was increased to 12?h, formation of the ring annulated product 4,5-dihydro-1H-pyrazole-1-carboximidamide was observed. This is the first case of ring-chain isomerism in conjugated guanylhydrazones. The acyclic conjugated guanylhydrazone and the corresponding annulated product (4,5-dihydro-1H-pyrazole-1-carboximidamide) could be clearly distinguished by means of UV and NMR spectroscopy. The formation of the ring isomer was further confirmed by single crystal XRD analysis. The time-dependent 1H NMR study indicated the gradual transformation of the open-chain compound into the cyclic one. The mechanistic insights into the formation of these two products were explored using quantum chemical methods which revealed that the ring isomer is thermodynamically more stable than the open-chain isomer by 6–11?kcal/mol and the barrier for cyclization was found to be 31.37?kcal/mol. 相似文献
110.
Trapti Joshi Tushar Jain Rohit Mahar Sumit K. Singh Piush Srivastava Sanjeev K. Shukla 《Natural product research》2018,32(4):430-434
The bioassay guided fractionation of methanolic extract of Murraya koenigii (L.) Spreng. leaves resulted in the isolation of seven pyranocarbazoles. These were evaluated against four bacterial strains and ten Candida sp. including two matched pair of fluconazole sensitive/resistant clinical isolates. Out of seven, three i.e. Koenine (mk279), Koenigine (mk309) and Mahanine (mk347) exhibited significant antibacterial activity MIC90 3.12–12.5 μg/mL against bacterial strains Streptococcus aureus and Klebsiella pneumonia compared with standard drug Kanamycin MIC90 12.5 μg/mL. However, only mk309 was found active against variety of Candida species MIC90 12.5–100 μg/mL. It was observed that hydroxylation at C-6 and C-7 positions in the studied pyranocarbazoles activate the bioactivity. Simultaneously, decrease in Log P value compares with ?H and ?O?CH3 substituted derivatives. The study is focused on selective antifungal and antibacterial activity of pyranocarbazoles on bacterial strains S. aureus, K. pneumonia and variety of Candida species with structure activity relationship observations. 相似文献