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991.
992.
The importance of studying mixed micellization lies in tuning the performance of an amphiphile to bend through variation of
stoichiometry of the blend. In this study, the binary and ternary mixed systems of cetylpyridinium chloride (CPC), tetradecyltrimethylammonium
bromide, and dodecylpyridinium chloride (DPC) have been studied at 30°C using tensiometry and conductometry. In most cases,
the cmc observed from either method is in close proximity whereas in CPC/DPC mixtures, tensometric cmc precedes conductometric
cmc which may arise from a lowering in degree of counterion binding on micellar interface in the mixed system with lower stoichiometric
mole fraction of CPC. Various existing theories have been used and the results were compared with the experimental observations. 相似文献
993.
994.
995.
Antonio Bauzá Dr. David Quiñonero Prof. Dr. Pere M. Deyà Prof. Antonio Frontera 《化学:亚洲杂志》2013,8(11):2708-2713
Sulfide:quinone oxidoreductase (SQR) is a flavin‐dependent enzyme that plays a physiological role in two important processes. First, it is responsible for sulfide detoxification by oxidizing sulfide ions (S2? and HS?) to elementary sulfur and the electrons are first transferred to flavin adenine dinucleotide (FAD), which in turn passes them to the quinone pool in the membrane. Second, in sulfidotrophic bacteria, SQRs play a key role in the sulfide‐dependent respiration and anaerobic photosynthesis, deriving energy for their growth from reduced sulfur. Two mechanisms of action for SQR have been proposed: first, nucleophilic attack of a Cys residue on the C4 of FAD, and second, an alternate anionic radical mechanism by direct electron transfer from Cys to the isoalloxazine ring of FAD. Both mechanisms involve a common anionic intermediate that it is stabilized by a relevant anion–π interaction and its previous formation (from HS? and Cys‐S‐S‐Cys) is also facilitated by reducing the transition‐state barrier, owing to an interaction that involves the π system of FAD. By analyzing the X‐ray structures of SQRs available in the Protein Data Bank (PDB) and using DFT calculations, we demonstrate the relevance of the anion–π interaction in the enzymatic mechanism. 相似文献
996.
Finite difference methods of O(h4) are proposed for obtaining estimates of first‐order partial derivatives of the solution of three‐dimensional quasi‐linear elliptic equation with mixed derivative terms subject to Dirichlet boundary conditions on a uniform cubic grid. In all the cases, we use a single computational cell and the methods are applicable to the problems both in cartesian and polar coordinates. The utility of the new methods is shown by testing the methods on three‐dimensional poisson solvers in polar coordinates. Some numerical examples are provided to demonstrate the accuracy and efficiency of the methods discussed. © 2000 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 16: 417–425, 2000 相似文献
997.
Chantalle J. Krajewska Sen R. Kavanagh Lina Zhang Dominik J. Kubicki Krishanu Dey Krzysztof Gakowski Clare P. Grey Samuel D. Stranks Aron Walsh David O. Scanlon Robert G. Palgrave 《Chemical science》2021,12(44):14686
Lead-free halides with perovskite-related structures, such as the vacancy-ordered perovskite Cs3Bi2Br9, are of interest for photovoltaic and optoelectronic applications. We find that addition of SnBr2 to the solution-phase synthesis of Cs3Bi2Br9 leads to substitution of up to 7% of the Bi(iii) ions by equal quantities of Sn(ii) and Sn(iv). The nature of the substitutional defects was studied by X-ray diffraction, 133Cs and 119Sn solid state NMR, X-ray photoelectron spectroscopy and density functional theory calculations. The resulting mixed-valence compounds show intense visible and near infrared absorption due to intervalence charge transfer, as well as electronic transitions to and from localised Sn-based states within the band gap. Sn(ii) and Sn(iv) defects preferentially occupy neighbouring B-cation sites, forming a double-substitution complex. Unusually for a Sn(ii) compound, the material shows minimal changes in optical and structural properties after 12 months storage in air. Our calculations suggest the stabilisation of Sn(ii) within the double substitution complex contributes to this unusual stability. These results expand upon research on inorganic mixed-valent halides to a new, layered structure, and offer insights into the tuning, doping mechanisms, and structure–property relationships of lead-free vacancy-ordered perovskite structures.Mixed valence Sn doping of Cs3Bi2Br9 leads to broad visible light absorption. 相似文献
998.
Nitesh Kumawat Andrejs Tucs Soumen Bera Gennady N. Chuev Marat Valiev Marina V. Fedotova Sergey E. Kruchinin Koji Tsuda Adnan Sljoka Amit Chakraborty 《Molecules (Basel, Switzerland)》2022,27(3)
The entry of the SARS-CoV-2, a causative agent of COVID-19, into human host cells is mediated by the SARS-CoV-2 spike (S) glycoprotein, which critically depends on the formation of complexes involving the spike protein receptor-binding domain (RBD) and the human cellular membrane receptor angiotensin-converting enzyme 2 (hACE2). Using classical site density functional theory (SDFT) and structural bioinformatics methods, we investigate binding and conformational properties of these complexes and study the overlooked role of water-mediated interactions. Analysis of the three-dimensional reference interaction site model (3DRISM) of SDFT indicates that water mediated interactions in the form of additional water bridges strongly increases the binding between SARS-CoV-2 spike protein and hACE2 compared to SARS-CoV-1-hACE2 complex. By analyzing structures of SARS-CoV-2 and SARS-CoV-1, we find that the homotrimer SARS-CoV-2 S receptor-binding domain (RBD) has expanded in size, indicating large conformational change relative to SARS-CoV-1 S protein. Protomer with the up-conformational form of RBD, which binds with hACE2, exhibits stronger intermolecular interactions at the RBD-ACE2 interface, with differential distributions and the inclusion of specific H-bonds in the CoV-2 complex. Further interface analysis has shown that interfacial water promotes and stabilizes the formation of CoV-2/hACE2 complex. This interaction causes a significant structural rigidification of the spike protein, favoring proteolytic processing of the S protein for the fusion of the viral and cellular membrane. Moreover, conformational dynamics simulations of RBD motions in SARS-CoV-2 and SARS-CoV-1 point to the role in modification of the RBD dynamics and their impact on infectivity. 相似文献
999.
The present work concerns itself with the study of the effects of Growth Rate Dispersion (GRD) in industrial crystallizers. The GRD in crystallizers is described by a model similar to the one describes axial dispersion in near plug flow reactors. From it differential and cumulative equations are developed for crystal population, crystal length, crystal area, and crystal mass. The model results have been compared with the available experimental data of sucrose crystallizer. 相似文献
1000.
This work deals with the prediction of crystal size distribution (CSD) in a continuous crystallizer for size-dependent growth. Crystal growth rates are described by Abegg, Stevens, and Larson (ASL) model. Stratified Monte Carlo method has been employed to evaluate the integrals involved in the classical moment equation for prediction of CSD. The simulation results have been compared with the available experimental data of K2CO3 · 1.5 H2O crystals in a continuous crystall lizer. 相似文献