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排序方式: 共有418条查询结果,搜索用时 15 毫秒
91.
92.
Jyoti Malviya R. K. P. Singh Shashi Kala L. K. Sharma 《Russian Journal of Electrochemistry》2018,54(3):311-317
A facile and Eco-compatible synthesis of benzofuran derivatives (4a–4h) has been carried out at platinum electrode by electrochemical oxidation of catechol in the presence of active methylene groups. Electro- organic synthesis has been performed in an undivided cell at ambient conditions. The products of electrolysis have been purified and characterized by FTIR, 1H NMR and 13C NMR and mechanism was deduced by voltammetric studies. 相似文献
93.
94.
The mass spectral fragmentation of seven substituted 2,4,6-triaryl-s-trithianes has been studied and the fragmentation modes confirmed by deuterium labelling. Triphenyl-s-trithiane shows some interesting features in its mode of cleavage and does not eliminate S, S2, SH˙, H2S or S2H˙ from its molecular ion. The prominent radical ions in the mass spectrum are at m/e 180 (52.3%) and m/e 186 (45.2%), corresponding to stilbene and PhCHS3. Their compositions have been established by deuterium labelling and accurate mass measurements. The formation of stilbene indicates a relationship between pyrolytic and electron-impact studies. The origin of [PhCHS3]+˙ suggests that one of the sulphur atoms attaches itself to the other two sulphur atoms in the molecular ion, eliminating a stilbene radical ion. The other important fragmentation corresponds to the monomer radical ion (thiobenzaldehyde) and the thiobenzoyl cation. Among the other substituted triaryl-s-trithianes with substituents such as chloro, methoxy, methylenedioxy and hydroxy groups on the phenyl ring (IV to IX), only the tris-(p-chlorophenyl)-s trithiane shows an insignificant molecular ion. Unlike the triphenyl derivative, the chloro, methoxy and methylenedioxy derivatives show the loss of HS˙ and/or H2S from the molecular ion. The spectrum of tris-(p-hydroxyphenyl)-s-trithiane corresponds to the spectrum of p-hydroxythiobenzaldehyde. 相似文献
95.
Acharya S Barman J Cheruku P Chatterjee S Acharya P Isaksson J Chattopadhyaya J 《Journal of the American Chemical Society》2004,126(28):8674-8681
The pH titration and NMR studies (pH 6.6-12.5) in the heptameric isosequential ssDNA and ssRNA molecules, [d/r(5'-CAQ1GQ2AC-3', with variable Q1/Q2)], show that the pKa of the central G residue within the heptameric ssDNAs (DeltapKa = 0.67 +/- 0.03) and ssRNAs (DeltapKa = 0.49 +/- 0.02) is sequence-dependent. This variable pKa of the G clearly shows that its pseudoaromatic character, hence, its chemical reactivity, is strongly modulated and tuned by its sequence context. In contradistinction to the ssDNAs, the electrostatic transmission of the pKa of the G moiety to the neighboring A or C residues in the heptameric ssRNAs (as observed by the response of the aromatic marker protons of As or Cs) is found to be uniquely dependent upon the sequence composition. This demonstrates that the neighboring As or Cs in ssRNAs have variable electrostatic efficiency to interact with the central G/G-, which is owing to the variable pseudoaromatic characters (giving variable chemical reactivities) of the flanking As or Cs compared to those of the isosequential ssDNAs. The sequence-dependent variation of pKa of the central G and the modulation of its pKa transmission through the nearest-neighbors by variable electrostatic interaction is owing to the electronically coupled nature of the constituent nucleobases across the single strand, which demonstrates the unique chemical basis of the sequence context specificity of DNA or RNA in dictating the biological interaction, recognition, and function with any specific ligand. 相似文献
96.
The paper mathematically establishes that magnetorotatory thermohaline convection of the Veronis [7] type cannot manifest itself as oscillatory motions of growing amplitude in an initially bottom heavy configuration if the thermohaline Rayleigh numberR s, the Lewis number τ, the thermal Prandtl number σ, the magnetic Prandtl number σ1, the Chandrasekhar numberQ and the Taylor numberT satisfy the inequality \(R_s 4\pi ^4 \left[ {1 + \frac{\tau }{{\sigma \pi ^2 }}\left\{ {\pi ^2 - \left( {O\sigma _1 + \frac{T}{{\pi ^2 }}} \right)} \right\}} \right]\) when both the boundary surfaces are rigid thus achieving magnetorotatory extension of an important characterization theorem of Banerjeeet al (1992) on the corresponding hydrodynamic problem. A similar characterization theorem is mathematically established in the context of the magnetorotatory thermohaline convection of the Stern (1960) type. 相似文献
97.
Sandeep K. Vaishanav Jyoti Korram Rekha Nagwanshi Kallol K. Ghosh Manmohan L. Satnami 《Journal of fluorescence》2016,26(3):855-865
Protein Quantum dots interaction is crucial to investigate for better understanding of the biological interactions of QDs. Here in, the model protein Bovine serum albumin (BSA) was used to evaluate the process of protein QDs interaction and adsorption on QDs surface. The modified Stern-Volmer quenching constant (Ka), number of binding sites (n) at different temperatures (298 308 and 318 K?±?1) and corresponding thermodynamic parameters (ΔG?<?0, ΔH?<?0, and ΔS?>?0) were calculated. The quenching constant (Ks) and number of binding sites (n) is found to be inversely proportional to temperature. It signified that static quenching mechanism is dominant over dynamic quenching. The standard free energy change (ΔG?<?0) implies that the binding process is spontaneous, while the enthalpy change (ΔH?<?0) suggest that the binding of QDs to BSA is an enthalpy-driven process. The standard entropy change (ΔS?>?0) suggest that hydrophobic force played a pivotal role in the interaction process. The adsorption process were assessed and evaluated by pseudofirst-order, pseudosecond-order kinetic model, and intraparticle diffusion model. 相似文献
98.
Raghubir Singh Varinder Kaur Chahal Raj Pal Sharma Paloth Venugopalan 《Journal of organometallic chemistry》2010,695(2):183-1348
A novel silatrane containing Si ← N bond (2.160 Å), has been synthesized by the reaction of 3-aminopropylsilatrane (1), dicyclohexylcarbodiimide (2) and CS2. The structure was established by elemental analysis, spectroscopic methods (IR, 1H NMR, 13C NMR and Mass spectroscopy) and X-ray crystallography. It was correlated with theoretical studies such as semiempirical (AM1, PM3, PM3MM and MNDO), Density Functional Theory (B3LYP) and Hartree-Fock at 3-21+G∗ and 6-31G∗(d) levels. The reactivity of compound 3 was studied with some Lewis acids and bases that showed the formation of corresponding adducts (4-7), which were characterized by elemental analysis, IR and NMR (1H, 13C) spectroscopy. 相似文献
99.
This paper examines the relation between debt and corporate governance in emerging market economies. We use firm-level panel data of listed companies from Thailand and Indonesia to analyze the firm’s corporate financing behaviors in connection with its corporate governance arrangements. Our results show that the debt structure is linked to the corporate governance. We find that weaker corporate governance firms, in particular measured by the entrenchment effects, tend to have a higher debt level. The evidence is relatively stronger during the crisis period. Our results also shed lights on the importance of the country-specific institutional settings that would affect the empirical results. 相似文献
100.
Romen Singh Naorem Bandana Devi Pangabam Sudipta Sankar Bora Gunajit Goswami Madhumita Barooah Dibya Jyoti Hazarika Csaba Fekete 《Molecules (Basel, Switzerland)》2022,27(7)
Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen and responsible for causing life-threatening infections. The emergence of hypervirulent and multidrug-resistant (MDR) S. aureus strains led to challenging issues in antibiotic therapy. Consequently, the morbidity and mortality rates caused by S. aureus infections have a substantial impact on health concerns. The current worldwide prevalence of MRSA infections highlights the need for long-lasting preventive measures and strategies. Unfortunately, effective measures are limited. In this study, we focus on the identification of vaccine candidates and drug target proteins against the 16 strains of MRSA using reverse vaccinology and subtractive genomics approaches. Using the reverse vaccinology approach, 4 putative antigenic proteins were identified; among these, PrsA and EssA proteins were found to be more promising vaccine candidates. We applied a molecular docking approach of selected 8 drug target proteins with the drug-like molecules, revealing that the ZINC4235426 as potential drug molecule with favorable interactions with the target active site residues of 5 drug target proteins viz., biotin protein ligase, HPr kinase/phosphorylase, thymidylate kinase, UDP-N-acetylmuramoyl-L-alanyl-D-glutamate-L-lysine ligase, and pantothenate synthetase. Thus, the identified proteins can be used for further rational drug or vaccine design to identify novel therapeutic agents for the treatment of multidrug-resistant staphylococcal infection. 相似文献