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991.
Adepu R Rambabu D Prasad B Meda CL Kandale A Krishna GR Reddy CM Chennuru LN Parsa KV Pal M 《Organic & biomolecular chemistry》2012,10(29):5554-5569
Novel thieno[2,3-d]pyrimidines containing a cyclohexane ring fused with a six- or five-membered heterocyclic moiety along with a benzylic nitrile were designed as potential inhibitors of PDE4. Expeditious synthesis of these compounds was carried out via a multi-step sequence consisting of a few key steps such as Gewald reaction, Dieckmann type cyclisation and Krapcho decarboxylation. This newly developed strategy involved construction of the thienopyrimidine ring followed by the cyclohexanone moiety and subsequently the fused heterocyclic ring. A number of thieno[2,3-d]pyrimidine based derivatives were synthesized using this method some of which showed promising PDE4B inhibitory properties. One of them was tested for PDE4D inhibition in vitro and dose dependent inhibition of TNF-α. A few selected molecules were docked into the PE4B protein the results of which showed good overall correlations to their observed PDE4B inhibitory properties in vitro. The crystal structure analysis of representative compounds along with hydrogen bonding patterns and molecular arrangement present within the molecule is described. 相似文献
992.
A short and efficient approach to a 4-methylene-2-cyclohexenone substructure present in otteliones and loloanolides is described. This strategy involves a tandem enyne/ring closing metathesis as the key reaction to construct this labile core unit. 相似文献
993.
Ch. Rajyasree P. Srinivasa Rao P.M. Vinaya Teja A. Ramesh Babu S. Yusub D. Krishna Rao 《Journal of Non》2012,358(18-19):2597-2605
Transparent glasses of composition 10BaO.20Bi2O3.(70 ? x)B2O3.xFe2O3 (wt.%) where 0 ≤ x ≤ 2.0, were characterized by XRD and SEM. Physical, spectroscopic and dielectric properties were investigated. At higher dopant of Fe2O3, EPR results revealed that, the number of Fe3+ ions participate in the resonance is decreased by forming a new signal at g ≈ 3.015 due to increase of antiferromagnetic interaction of Fe3+ ions and/or formation of low spin Fe3+ ions in the glass matrix. With initial 0.5 wt.% doping of Fe2O3, less dense glass is formed with colloids of metallic Bi0 atoms. The absorption bands at 604 and 712 nm in F5 glass are ascribed to Bi0 and Bi+ radicals respectively. No characteristic Fe3+ absorption bands (spin-forbidden) are found. Fe2+ ions are increased at higher concentration of Fe2O3. Higher concentration of Fe2O3 is favorable for BO2O?, BO3, BiO6 and FeO6 symmetry unit leads to low band gap and high Urbach energy. By doping of Fe2O3 the dielectric parameters like dielectric constant (ε′), loss (tanδ and ac electrical conductivity (σac) are found to increase. 相似文献
994.
E.D. D'silva G. Krishna Podagatlapalli S. Venugopal Rao S.M. Dharmaprakash 《Optics & Laser Technology》2012,44(6):1689-1697
A new nonlinear optical (NLO) organic crystal 1-[4-({(E)-[4-(methylsulfanyl)phenyl]methylidene}amino)phenyl]ethanone (MMP) has been grown by slow evaporation technique at ambient temperature. The crystal structure of MMP was determined by single crystal X-ray diffraction. MMP crystallizes in non-centrosymmetric monoclinic system with space group P21. The FT-IR spectrum recorded for new crystal confirmed the presence of various functional groups in the material. MMP was found to be thermally stable up to 300 °C. The grown crystal was optically transparent in the wavelength range of 400–1100 nm. The second harmonic generation (SHG) efficiency of the crystal was measured by the classical powder technique using Nd:YAG laser and was found to be 4.13 times more efficient than reference material, urea. Third order nonlinear parameters were measured by employing the Z-scan technique. The laser damage threshold for MMP crystal was determined to be 4.26 GW/cm2. The Brewster angle technique was employed to measure the refractive index of the crystal and the values for green and red wavelengths were found to be 1.35 and 1.33, respectively. The dielectric and electrical measurements were carried out to study the different polarization mechanisms and conductivity of the crystal. 相似文献
995.
Full-field out-of-plane deformation measurement of specular surfaces can be implemented quickly and conveniently using fringe reflectometry. The system configuration is simple and processing is fast. With the assistance of an advanced fringe pattern processing technique, the windowed Fourier ridges method, only a single two-directional fringe pattern is necessary for determination of the deformed surface profile. Thus, the whole measurement only requires a single image with the potential for high speed or even real time measurement. 相似文献
996.
K. Shadak Alee M. Bala Murali Krishna B. Ashok D. Narayana Rao 《Photonics and Nanostructures》2012,10(2):236-242
Enhancement of nonlinear absorption of polystyrene (PS) was investigated using 3D PS photonic crystals (PCs) with Z-scan technique. The Z-scan experiment was carried out at 532 nm in the picosecond (ps) regime. The transmittance of the PC was found to get modified because of the nonlinear absorption of PS particularly when 532 nm is near the photonic stop band (PSB) edge of PC. Calculations show that the field gets enhanced by 1.4 times the input field intensity within the crystal when the 532 nm wavelength falls at the PSB edge while keeping the crystal at an angle of 35°. 相似文献
997.
Reddi Mohan Naidu K Satheesh Krishna B Anil Kumar M Arulselvan P Ibrahim Khalivulla S Lasekan O 《Molecules (Basel, Switzerland)》2012,17(6):7543-7555
Polyethyleneglycol bound sulfonic acid (PEG-OSO?H), a chlorosulphonic acid-modified polyethylene glycol was successfully used as an efficient and eco-friendly polymeric catalyst in the synthesis of 14-aryl/heteroaryl-14H-dibenzo[a,j]xanthenes obtained from the reaction of 2-naphthol and carbonyl compounds under solvent-free conditions with short reaction times and excellent yields. The biological properties of these synthesized title compounds revealed that compounds 3b, 3c, 3f and 3i showed highly significant anti-viral activity against tobacco mosaic virus. 相似文献
998.
Structure, bonding, and lowest energy transitions in unsymmetrical squaraines: a computational study
Yesudas K Chaitanya GK Prabhakar Ch Bhanuprakash K Rao VJ 《The journal of physical chemistry. A》2006,110(41):11717-11729
Natural resonance theory (NRT) and natural bond orbital (NBO) analysis have been carried out on a simple symmetrical and an unsymmetrical substituted squaraine with a view of understanding the structure of the latter type of squaraines. It is found that there are some fundamental differences in the structure and bonding between these two types of squaraines particularly in the resonance weights and delocalization energies. These differences are expected to reflect in the low energy transitions and charge transfer in these squaraines. To investigate this, the nature of the lowest energy transitions occurring on excitation in unsymmetrical squaraines has been studied using high-level symmetry adapted cluster-configuration interaction method (SAC/SAC-CI) and compared with reported experimental observations. In general the agreement with the experimental data is very good. The transition dipole moment always lies on the pi-backbone and is quite large in magnitude. The ground state dipole moment in some cases does not change in the excited state upon excitation while in some other cases there is a large reduction/enhancement in the magnitude indicative of some charge rearrangement in this direction. Inclusion of the solvent using the IEFPCM model, a slightly better agreement with the experiment is found in some cases. Studies are carried out with a different basis set and it is found that the change in basis set has very little effect on the transition energies. In the case of weak side donor groups attached to the central ring the larger charge transfer to the central acceptor ring in general takes place from the O- atoms of the squarylium moiety while in the case of strong donors the charge transfer from the O- atoms to the central rings drop down. We have not observed any correlation between the charge transfer in the excited state to the central ring from the side donor groups and the lowest energy excitation in the molecules. Reduction of the HOMO-LUMO gap (an indication of increase of the diradicaloid character) always leads to a bathochromic shift. 相似文献
999.
The impact of basis set superposition error (BSSE) upon molecular properties determined using the density functionals B3LYP, B3PW91, B3P86, BLYP, BPW91, and BP86 in combination with the correlation consistent basis sets [cc-pVnZ, where n = D(2), T(3), Q(4), and 5] for a set of first-row closed-shell molecules has been examined. Correcting for BSSE enables the irregular convergence behavior in molecular properties such as dissociation energies with respect to increasing basis set size, noted in earlier studies, to be improved. However, for some molecules and functional combinations, BSSE correction alone does not improve the irregular convergence behavior. 相似文献
1000.
We report gold nanoparticle based FRET assay to monitor the cleavage of DNA by nucleases. Fluorescence signal enhancement is observed by a factor of 120 after the cleavage reaction in the presence of S1 nuclease. The mechanism of distant dependent fluorescence quenching has been discussed. Our experimental results on distance dependent fluorescence quenching match quite well with theoretical findings obtained from the fluorescence quenching model by Gersten and Nitzan (Surf. Sci. 1985, 158, 165). Our experimental observation paradigm for the design of optical based molecular ruler strategies at distances more than double the distances achievable using traditional dipole-dipole Columbic energy transfer based methods. 相似文献