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31.
32.
Zusammenfassung Auf Grund von Symmetrieüberlegungen wurden aus den kürzlich erhaltenen Schwingungs- und Strukturdaten des Dichlorfluoramins und des Difluorchloramins, die beide Cs-Symmetrie besitzen, Schwingungskonstanten, wie die Schwingungskraftkonstanten und die mittleren Schwingungsamplituden, spektroskopisch ermittelt. Die Bindungskraftkonstanten der genannten Moleküle wurden unter Verwendung eines Bindungskraftfeldes von sechs Konstanten errechnet. Weiters wurden die mittleren Schwingungskonstanten sowohl der gebundenen als auch der nichtgebundenen Atompaare für Zimmertemperatur berechnet. Schließlich wurden unter Annahme eines starren Rotators und harmonischen Oszillators die statistischen thermodynamischen Funktionen für den Temperaturebereich von 200–2000° K berechnet. Eine kurze Diskussion ist angeschlossen.
Mit 1 Abbildung 相似文献
Vibrational constants and thermodynamic functions of difluorochloramine and dichlorofluoramine
On the basis of symmetry considerations, vibrational constants such as valence force constants and mean amplitudes of vibration have been spectroscopically evaluated from the recent vibrational and structural data for NF2Cl and NCl2F possessing a Cs symmetry. Valence force constants by employing a six-constant valence force field and mean amplitudes of vibration for both bonded and nonbonded atom pairs at the room temperature have been computed for these molecules. In addition to these, statistical thermodynamic functions have
Mit 1 Abbildung 相似文献
33.
Han S Caspers N Zaniewski RP Lacey BM Tomaras AP Feng X Geoghegan KF Shanmugasundaram V 《Journal of the American Chemical Society》2011,133(50):20536-20545
Multi-drug-resistant forms of the Gram-negative pathogen Acinetobacter baumannii are an emerging threat to human health and further complicate the general problem of treating serious bacterial infections. Meeting this challenge requires an improved understanding of the relationships between the structures of major therapeutic targets in this organism and the activity levels exhibited against it by different antibiotics. Here we report the first crystal structures of A. baumannii penicillin-binding proteins (PBPs) covalently inactivated by four β-lactam antibiotics. We also relate the results to kinetic, biophysical, and computational data. The structure of the class A protein PBP1a was solved in apo form and for its covalent conjugates with benzyl penicillin, imipenem, aztreonam, and the siderophore-conjugated monocarbam MC-1. It included a novel domain genetically spliced into a surface loop of the transpeptidase domain that contains three conserved loops. Also reported here is the first high-resolution structure of the A. baumannii class B enzyme PBP3 in apo form. Comparison of this structure with that of MC-1-derivatized PBP3 of Pseudomonas aeruginosa identified differences between these orthologous proteins in A. baumannii and P. aeruginosa. Thermodynamic analyses indicated that desolvation effects in the PBP3 ligand-binding sites contributed significantly to the thermal stability of the enzyme-antibiotic covalent complexes. Across a significant range of values, they correlated well with results from studies of inactivation kinetics and the protein structures. The structural, biophysical, and computational data help rationalize differences in the functional performance of antibiotics against different protein targets and can be used to guide the design of future agents. 相似文献
34.
Marudachalam Shanmugasundaram Mrinalini Puranik 《Journal of Raman spectroscopy : JRS》2009,40(12):1726-1748
Purines, pyrimidines, and the corresponding ribose monophosphates are ubiquitous biomolecules involved in several cellular processes–in DNA and RNA, signaling, and energy transactions. In the new and exciting field of DNA‐inspired nanostructures, they are used as fundamental building blocks. Unique features of the nucleobases are that several tautomeric states are close in energy and the tautomeric equilibria are sensitive to exocyclic substitution and pH. Knowing the exact structure and tautomer(s) at physiological conditions is crucial to understand the substrate specificities and catalytic mechanisms of the many enzymes for which these nucleobases are substrates. Very few spectroscopic methods can distinguish between tautomers and provide solution structures. Vibrational spectroscopy has long been known to be an excellent tool to obtain reliable information on nucleic acids. However, even when good‐quality spectra are available, isotope editing is required to make reliable band assignments and identify structures unequivocally. Density functional theoretical (DFT) methods have become indispensible in assisting the assignment of observed spectra to normal modes, identification of tautomers, and modeling of spectra of isotope‐edited molecules. We review the performance of DFT methods in the prediction of nucleobases and their analogs. We find that even with modest basis sets, trends in vibrational spectra can be predicted adequately and guide assignments to normal modes of the molecule. Shifts in band positions induced upon isotope labeling are reproduced more reliably than the band positions. Scaling considerably improves the agreement between the computed and experimental spectra, but accurate prediction of vibrations of exocyclic groups like CO requires that solvent effects are taken into account. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
35.
Shanmugasundaram Rajasri Shankramma Kalikeri Subramanian Balachandran Kaliyamoorthy Gowthami Ganesamoorthy Thirunarayanan Meenakshisundaram Swaminathan Inbasekaran Muthuvel 《印度化学会志》2022,99(3):100337
Photocatalysis has recently been regarded as one of the most viable technologies for water treatment. Scholars all over the world are focusing on nanocomposites for water treatment for efficient and effective sanitization of bodies of water. Because of their high surface area, high chemical reactivity, excellent mechanical strength, low cost, and nanoscale composite materials have enormous potential to purify water in a various way. In this study, n-type TiO2 was synthesized and tailored to produce a TiO2/BiOI n–p nanocatalyst for enhanced photodegradation of 2,4-dinitrophenol (2,4-DNP) under UV-A and solar light respectively. Because of the formation of a heterojunction between BiOI and TiO2, the photocatalytic activity in TiO2/BiOI absorbs strongly in both the UV and visible regions and it has a lower recombination rate of the e-/h+ pairs. Furthermore, the generation of OH?, O2?– radicals during the oxidation process is attributed to the photodegradation of 2,4-DNP. The results revealed that the TiO2/BiOI manifest outperformed BiOI and TiO2 in terms of photocatalytic function. XRD, BET, HR-SEM-EDX with ECM, HR-TEM, FT-IR, PL, and UV-DRS techniques determined the photocatalyst composition. The HR-SEM images clearly showed that the particles are less than 27 ?nm in size. Thus, nanocomposite materials have played an important role in water purification. 相似文献
36.
Muthian Shanmugasundaram Raghavachary Raghunathan Ezekiel J. Padma Malar 《Heteroatom Chemistry》1998,9(5):517-522
Synthesis of a series of novel 1,3,2′-triphenyl-4-aryl spiropyrazolines [5.4′]-2′-butenolides has been accomplished in good yield by regioselective 1,3-dipolar cycloaddition of diphenylnitrilimine with (E)-3-arylidenebutenolides. X-ray crystal structure analysis of one of the products 4a confirms the structure of the product and the regiochemistry of cycloaddition. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9:517–522, 1998 相似文献
37.
Selvaraj Sureshkumar Shanmugasundaram Suguna Maruthamuthu Murugan Venkidasamy Baskar Shanmugasundaram Sambandam 《Journal of Cluster Science》2021,32(6):1507-1518
Journal of Cluster Science - Nanoparticles synthesized from biopolymers have received attention for their use as biological carriers in the delivery of hydrophobic drugs. Alginate, a marine... 相似文献
38.
Muthian Shanmugasundaram Annamalai Senthilvelan Anilkumar R. Kore 《Tetrahedron letters》2019,60(2):157-160
The Michael addition of pseudouridine with various propiolates in the presence of DBU as a base and DMF as a solvent is described. It is noteworthy that the reaction is highly regio- and stereoselective and affords (E)-pseudouridine-N1-acrylate in good yields with high purities. 相似文献
39.
Gopalan Anantha Iyengar Kyung Ryeol Ko Se-Hee Lee Komathi Shanmugasundaram Miklos Veres Kwang-Pill Lee 《Radiation Physics and Chemistry》2012,81(9):1407-1410
New poly(vinylidene fluoride) based multi-functional (electroconductive, bioactive and catalytic) nano-biowebs were prepared through gamma radiation induced formation of silica and gold nanoparticles (Au NPs) within electrospun (poly vinylidene fluoride) nanofiberous membranes. The multifunctional membrane is designated as PVdF@silica/Au ESNFM. The morphology of PVdF@silica/Au ESNFM was examined by field emission scanning electron microscopy. The presence of Au particles was confirmed by energy dispersive x-ray analysis. The crystal structure of Au particles and the formation of silica were confirmed by X-ray diffraction analysis. The multi-functionalities (electroconductive, bioactive and catalytic) of the nano-webs were evaluated by cyclic voltammetry. Cytochrome c was immobilized to generate nano-bioweb (PVdF@silica/Au/cyt c ESNFM), which exhibited electrochemical responses to nitrite ions. 相似文献
40.
Thanjam S Philips MF Komathi S Manisankar P Sivakumar C Gopalan A Lee KP 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2011,79(5):1256-1266
Kinetics of chemical oxidative polymerization of 4-aminodiphenylamine (4ADPA) was followed in aqueous 1 M p-toluene sulfonic acid (p-TSA) using silver nitrate (AgNO3) as an oxidant by UV-vis spectroscopy. The medium was found to be clear and homogeneous during the course of polymerization. The absorbances corresponding to the intermediate and the polymer were followed for different concentrations of 4ADPA and AgNO3 and at different reaction time. The appearance of a band around 450 nm during the initial stages of polymerization corresponds to the plasmon resonance formed by the reduction of Ag+ ions. Rate of poly(4-aminodiphenylamine)/Ag nanocomposite (RP4ADPA/AgNC) was determined for various reaction conditions. R(P4ADP/AgNC) showed second order power dependence on 4ADPA and first order dependence on AgNO3. The observed order dependences of 4ADPA and AgNO3 on the formation of P4ADPA/AgNC were used to deduce a rate equation for the reaction. Rate constant for the reaction was determined through different approaches. The good agreement between the rate constants obtained through different approaches justifies the selection of rate equation. 相似文献