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971.
Temperature dependence of solvation dynamics and fluorescence anisotropy decay of 8-anilino-1-naphthalenesulfonate (ANS) bound to a protein, bovine serum albumin (BSA), are studied. Solvation dynamics of ANS bound to BSA displays a component (300 ps) which is independent of temperature in the range of 278-318 K and a long component which decreases from 5800 ps at 278 K to 3600 ps at 318 K. The temperature independent part is ascribed to a dynamic exchange of bound to free water with a low barrier. The temperature variation of the long component of solvation dynamics corresponds to an activation energy of 2.1 kcal mol(-1). The activation energy is ascribed to local segmental motion of the protein along with the associated water molecules and polar residues. The time scale of solvation dynamics is found to be very different from the time scale of anisotropy decay. The anisotropy decays are analyzed in terms of the wobbling motion of the probe (ANS) and the overall tumbling of the protein. 相似文献
972.
Dipak K. Dutta J. Derek Woollins Dilip Konwar Pravat Bhattacharyya 《Journal of organometallic chemistry》2006,691(6):1229-1234
The chelate complexes of the types (1) and (2) have been synthesized and characterized by IR and NMR spectroscopy. The lower shift of the ν(P-Se) bands and downfield shift of the 31P-{1H}NMR signals for both P(III) and P(V) atoms in 1 and 2 compared to the corresponding free ligands indicate chelate formation through selenium donor. 1 and 2 show terminal ν(CO) bands at 1977 and 1981 cm−1, respectively, suggesting high electron density at the metal center. The molecular structure of 2 has been determined by single-crystal X-ray diffraction. The rhodium atom is at the center of a square planar geometry having the phosphorus and selenium atoms of the chelating ligand at cis-position, one carbonyl group trans- to selenium and one chlorine atom trans- to phosphorus atom. 1 and 2 undergo oxidative addition (OA) reaction with CH3I to produce acyl complexes (3) and (4), respectively. The kinetics of the OA reactions reveal that 1 undergoes faster reaction by about 4.5 times than 2. The catalytic activity of 1 and 2 in carbonylation of methanol was higher than that of the well known species [Rh(CO)2I2]− and 2 shows higher catalytic activity compared to 1. 相似文献
973.
M. F. Beatty R. Bhattacharyya S. Sarangi 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2009,60(5):971-1006
A constitutive theory for a general class of incompressible, isotropic stress-softening, limited elastic rubberlike materials
is introduced. The model is applied to study the small amplitude, free longitudinal vibrational frequency of a load about
a suspended static equilibrium stretch of a finitely deformed, stress-softening spring with limiting extensibility. A number
of physical results, including bounds on the frequency, are reported. It is proved, for example, that the normalized vibrational
frequency for the ideally elastic neo-Hookean oscillator is a lower bound for the normalized frequency of every incompressible,
isotropic stress-softening, limited elastic oscillator within the general class. All results are illustrated for the special
limited elastic Gent and the purely elastic Demiray biomaterial models, both with stress-softening characterized by a Zú?iga–Beatty
front factor damage function. The results for both stress-softening models are compared with experimental data for several
gum rubbers and thoracic aortic tissue provided by others; and, overall, it is found that the stress-softening, limited elastic
Gent model best characterizes the data. 相似文献
974.
Sheo Mukund Suresh Yarlagadda Soumen Bhattacharyya S.G. Nakhate 《Journal of Quantitative Spectroscopy & Radiative Transfer》2012,113(16):2004-2008
The investigation on B2Σ+–X2Σ+ system of ScO was extended to higher vibrational levels by laser-induced fluorescence (LIF) spectroscopy in a free-jet. We have observed rotationally resolved excitation spectra for (4,0), (3,0), (2,0), and (1,2) bands in addition to the previously observed (0,0) and (1,0) bands. The wavenumbers of these bands were fitted to a Hamiltonian matrix to determine the molecular constants for the vibrational levels up to ν′=4 of the B2Σ+ state and ν″=2 of the X2Σ+ state. In addition, the vibration constants of the ground states were determined from the dispersed fluorescence wavenumbers between B2Σ+ (ν′=0–4) and X2Σ+ (ν″=0–8) transitions. The equilibrium molecular constants, derived from the extensive set of molecular constants for individual vibrational levels, were used to construct RKR potential energy curves for both the electronic states. The Franck–Condon factors were also calculated for the B2Σ+–X2Σ+ transition. 相似文献
975.
Minghui Gui Vasile Smuleac Lindell E. Ormsbee David L. Sedlak Dibakar Bhattacharyya 《Journal of nanoparticle research》2012,14(5):861
The potential for using hydroxyl radical (OH?) reactions catalyzed by iron oxide nanoparticles (NPs) to remediate toxic organic compounds was investigated. Iron oxide NPs were synthesized by controlled oxidation of iron NPs prior to their use for contaminant oxidation (by H2O2 addition) at near-neutral pH values. Cross-linked polyacrylic acid (PAA) functionalized polyvinylidene fluoride (PVDF) microfiltration membranes were prepared by in situ polymerization of acrylic acid inside the membrane pores. Iron and iron oxide NPs (80–100 nm) were directly synthesized in the polymer matrix of PAA/PVDF membranes, which prevented the agglomeration of particles and controlled the particle size. The conversion of iron to iron oxide in aqueous solution with air oxidation was studied based on X-ray diffraction, Mössbauer spectroscopy and BET surface area test methods. Trichloroethylene (TCE) was selected as the model contaminant because of its environmental importance. Degradations of TCE and H2O2 by NP surface generated OH? were investigated. Depending on the ratio of iron and H2O2, TCE conversions as high as 100 % (with about 91 % dechlorination) were obtained. TCE dechlorination was also achieved in real groundwater samples with the reactive membranes. 相似文献
976.
The effects of discontinuously time-varying perturbations on the dynamics of a particle moving in harmonic, symmetric double well and symmetric triple well potentials, are investigated both classically and quantum mechanically. The quantum dynamics is followed using the time-dependent Fourier grid Hamiltonian (TDFGH) method while the classical dynamics is analyzed within the framework of classical Hamiltonian mechanics. Depending on the spatial symmetry of the perturbation and the characteristic features of the reversal time , different types of ‘phase space’ structures are observed in each of the potentials. For symmetric double and triple well potentials, quantum dynamics reveals that complete destruction of tunnelling (CDT) can be achieved in the presence of a time-dependent spatially asymmetric perturbing field that is continuous in time. Any discontinuity in time-variation of the perturbation may induce over the barrier transition. The relevance of these results in the context of (i) tunnelling control and (ii) quantum computing with 3-state or 2-state quantum registers is briefly discussed. 相似文献
977.
Niharika Keot Bittu Lama Haobam Kisan Singh Himangshu Pratim Bhattacharyya Dr. Manabendra Sarma 《Chemphyschem》2023,24(23):e202300413
The importance of noncovalent interaction has gained attention in various domains covering drug and novel catalyst design. The present study mainly characterizes the role of hydrogen bond (H-bond) and other intermolecular interactions in different (1 : 1) complex analogues formed between the N-aryl-thiazol-2-ylidene (YR) and five proton donor (HX) molecules. The analysis of the singlet-triplet energy gap ( ) confirmed the stability of the singlet state for this class of N-aryl-thiazol-2-ylidenes than the triplet state. The interaction energy values of the YR-HX complexes follow the order: YR-NH3<YR-HCN<YR-H2O<YR-MeOH<YR-HF. In addition, substituting the H-atom of the N−H bond with bulky groups (−R) leads to an increase in the interaction energy of the YR-HX complexes. Hence, it was found that the replacement of N-atom in N-heterocyclic carbene (NHC) by S-atom forming N-aryl-thiazol-2-ylidene results in comparable intermolecular interactions with proton donor molecules similar to imidazole-2-ylidene (NHC). The current study enlightened the role of noncovalent interactions in carbene complexes with proton donor molecules. We hope that our work on carbene chemistry will pave the way for its application in the designing and synthesis of efficient catalysts. 相似文献
978.
Surajit Mondal Supriti Dutta Santanu Mal Swapan K. Pati Sayan Bhattacharyya 《Angewandte Chemie (International ed. in English)》2023,62(18):e202301269
The immiscibility of crystallographic facets in multi-metallic catalysts plays a key role in driving the green H2 production by water electrolysis. The lattice mismatch between tetragonal In and face-centered cubic (fcc) Ni is 14.9 % but the mismatch with hexagonal close-packed (hcp) Ni is 49.8 %. Hence, in a series of Ni−In heterogeneous alloys, In is selectively incorporated in the fcc Ni. The 18–20 nm Ni particles have 36 wt % fcc phase, which increases to 86 % after In incorporation. The charge transfer from In to Ni, stabilizes the Ni0 state and In develops a fractional positive charge that favors *OH adsorption. With only 5 at% In, 153 mL h−1 H2 is evolved at −385 mV with mass activity of 57.5 A g−1 at—400 mV, 200 h stability at −0.18 V versus reversible hydrogen electrode (RHE), and Pt-like activity at high current densities, due to the spontaneous water dissociation, lower activation energy barrier, optimal adsorption energy of OH− ions and the prevention of catalyst poisoning. 相似文献
979.
Dr. Hye Won Moon Dr. Feng Wang Dr. Kalishankar Bhattacharyya Dr. Oriol Planas Dr. Markus Leutzsch Dr. Nils Nöthling Dr. Alexander A. Auer Dr. Josep Cornella 《Angewandte Chemie (International ed. in English)》2023,62(49):e202313578
Organobismuth-catalyzed transfer hydrogenation has recently been disclosed as an example of low-valent Bi redox catalysis. However, its mechanistic details have remained speculative. Herein, we report experimental and computational studies that provide mechanistic insights into a Bi-catalyzed transfer hydrogenation of azoarenes using p-trifluoromethylphenol ( 4 ) and pinacolborane ( 5 ) as hydrogen sources. A kinetic analysis elucidated the rate orders in all components in the catalytic reaction and determined that 1 a (2,6-bis[N-(tert-butyl)iminomethyl]phenylbismuth) is the resting state. In the transfer hydrogenation of azobenzene using 1 a and 4 , an equilibrium between 1 a and 1 a ⋅ [OAr]2 (Ar=p-CF3−C6H4) is observed, and its thermodynamic parameters are established through variable-temperature NMR studies. Additionally, pKa-gated reactivity is observed, validating the proton-coupled nature of the transformation. The ensuing 1 a ⋅ [OAr]2 is crystallographically characterized, and shown to be rapidly reduced to 1 a in the presence of 5 . DFT calculations indicate a rate-limiting transition state in which the initial N−H bond is formed via concerted proton transfer upon nucleophilic addition of 1 a to a hydrogen-bonded adduct of azobenzene and 4 . These studies guided the discovery of a second-generation Bi catalyst, the rate-limiting transition state of which is lower in energy, leading to catalytic transfer hydrogenation at lower catalyst loadings and at cryogenic temperature. 相似文献
980.
We consider a modified electrokinetic model to study the electrophoresis of a hydrophobic particle by considering the finite sized ions. The mathematical model adopted in this study incorporates the ion steric repulsion, ion-solvent interactions as well as Maxwell stress on the electrolyte. The dielectric permittivity and viscosity of the electrolyte is considered to vary with the local ionic volume fraction. Based on this modified model for the electrokinetics we have analyzed the electrophoresis in a single as well as mixture of electrolytes of monovalent and non- electrolytes. The dependence of viscosity on local ionic volume fraction modifies the hydrodynamic drag as well as diffusivity of ions, which are ignored in existing studies on electrophoresis. A simplified model for electrophoresis of a hydrophobic particle incorporating the ion steric repulsion and ion-solvent interactions is developed based on the first-order perturbation on applied electric field. This simplified model is established to be efficient for a Debye layer thinner than the particle size and a smaller range of slip length. This model can be implemented for any number of ionic species as well as non- electrolytes. It is established that the ion steric interactions and dielectric decrement creates a counterion saturation in the Debye layer leading to an enhanced mobility compared to the standard model. However, experimental data for non-dilute cases often under predicts the theoretically determined mobility. The present modified model fills this lacuna and demonstrate that the consideration of finite ion size modifies the medium viscosity and hence, ionic mobility, which in combination lowers the mobility value. 相似文献