A model study on the mechanism and kinetics for the dissociation of water anion

Quantum chemical computations using both density functional theory (B3LYP functional) and wavefunction (MP2 and CCSD(T)) methods, with the 6-311++G(3df,2p) and aug-cc-pVnZ (n = D,T,Q) basis sets, in conjunction with a polarizable continuum model (PCM) method for treating structures in solution, were carried out to look again at a series of small negatively charged water species [(H₂O)_n]^•–. For each size n of [(H₂O)_n]^•– in aqueous solution with n = 2, 3, and 4, two distinct structural motifs can be identified: a classical water radical anion formed by hydrogen bonds and a molecular pincer in which the excess electron is directly interacting with H atoms. In aqueous solution, both motifs have comparable energy content and likely coexist and compete for the ground state. Some water anion isomers can dissociate when interaction with a water molecule, [(H₂O)_n]^•– + H₂O → H^•(H₂O)_m + OH^–(H₂O)_n–m, through successive hydrogen transfers with moderate energy barriers. This reaction can also be regarded as a water-splitting process in which the H transfers involved take place mainly within a water trimer, whereas other water molecules tend to stabilize transition structures through microsolvation rather than direct participation. Calculated absolute rate constants for the reversed reaction H^•(H₂O)₂ + OH^–(H₂O)₂ → [(H₂O)₄]^•־ + H₂O with both H and D isotopes agree well with the experimentally evaluated counterpart and lend a kinetic support for the involvement of a tetramer unit.     

Synthesis and antifungal activity of chitosan-silver nanocomposite synergize fungicide against Phytophthora capsici

Fungicides are important tools for preventing pathogens and maintaining crop quality; however, their effectiveness was directly affected by high-priced, toxicity, and environmental pollution. As a result, it is necessary to get a safe and efficient antimicrobial agent against agricultural pathogens. In this study, silver-incorporated chitosan nanocomposites (Ag@CS) were first prepared in which CS was used as reducing and stabilizing agent and then these nanocomposites was synergized with fungicide Antracol (An), Ag@CS/An, against Phytophthora capsici causing Phytophthora blight in pepper. The obtained nanocomposites were characterized by Fourier transform infrared (FTIR), X-ray diffraction analysis (XRD), thermogravimetric analysis (TGA), dynamic light scattering (DLS), and transmission electron microscopy (TEM). These results showed that Ag@CS and Ag@CS/An were successfully synthesized with spherical shape AgNPs having diameter of 20.3?±?0.7?nm and 44.6?±?0.3?nm, respectively. More importantly, Ag@CS/An was found to have significantly stronger antifungal ability than each component alone, analyzed by agar diffusion method. It might be anticipated that Ag@CS/An has a promising future as nano-antibiotic materials for agriculture.     

Discovery of small molecular inhibitors for interleukin-33/ST2 protein–protein interaction: a virtual screening,molecular dynamics simulations and binding free energy calculations

The interleukin-1 receptor like ST2 has emerged as a potential drug discovery target since it was identified as the receptor of the novel cytokine IL-33, which is involved in many inflammatory and autoimmune diseases. For the treatment of such IL-33-related disorders, efforts have been made to discover molecules that can inhibit the protein–protein interactions (PPIs) between IL-33 and ST2, but to date no drug has been approved. Although several anti-ST2 antibodies have entered clinical trials, the exploration of small molecular inhibitors is highly sought-after because of its advantages in terms of oral bioavailability and manufacturing cost. The aim of this study was to discover ST2 receptor inhibitors based on its PPIs with IL-33 in crystal structure (PDB ID: 4KC3) using virtual screening tools with pharmacophore modeling and molecular docking. From an enormous chemical space ZINC, a potential series of compounds has been discovered with stronger binding affinities than the control compound from a previous study. Among them, four compounds strongly interacted with the key residues of the receptor and had a binding free energy?<????20 kcal/mol. By intensive calculations using data from molecular dynamics simulations, ZINC59514725 was identified as the most potential candidate for ST2 receptor inhibitor in this study.

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Surface Modification of Cellulose Microfibrils with Silane Agent for Eco-Friendly Hydrophobic Coatings

Russian Journal of Applied Chemistry - In this study, an optimized method for surface modification of cellulose microfibrils (CMF) with (3-Aminopropyl) trimethoxysilane (APTMS) for eco-friendly...     

Full‐Order observer design for nonlinear complex large‐scale systems with unknown time‐varying delayed interactions

This article is concerned with the problem of state observer for complex large‐scale systems with unknown time‐varying delayed interactions. The class of large‐scale interconnected systems under consideration is subjected to interval time‐varying delays and nonlinear perturbations. By introducing a set of argumented Lyapunov–Krasovskii functionals and using a new bounding estimation technique, novel delay‐dependent conditions for existence of state observers with guaranteed exponential stability are derived in terms of linear matrix inequalities (LMIs). In our design approach, the set of full‐order Luenberger‐type state observers are systematically derived via the use of an efficient LMI‐based algorithm. Numerical examples are given to illustrate the effectiveness of the result. © 2014 Wiley Periodicals, Inc. Complexity 21: 123–133, 2015     

Mechanism of oligomerization reactions of silica

The mechanism of the oligomerization reaction of silica, the initial step of silica formation, has been studied by quantum chemical techniques. The solvent effect is included by using the COSMO model. The formation of various oligomers (from dimer to tetramer) was investigated. The calculations show that the anionic pathway is kinetically preferred over the neutral route. The first step in the anionic mechanism is the formation of the SiO-Si linkage between the reactants to form a five-coordinated silicon complex, which is an essential intermediate in the condensation reaction. The rate-limiting step is water removal leading to the oligomer product. The activation energies for dimer and trimer formation ( approximately 80 kJ/mol) are significantly higher than those of the subsequent oligermerization. The activation energies for the ring closure reaction ( approximately 100 kJ/mol) are even higher. The differences in activation energies can be related to the details in intra- and intermolecular hydrogen bonding of the oligomeric complexes.     

Langmuir and Langmuir–Blodgett Films from Amphiphilic Pillar[5]arene‐Containing [2]Rotaxanes

Amphiphilic pillar[5]arene‐containing [2]rotaxanes have been prepared and fully characterized. In the particular case of the [2]rotaxane incorporating a 1,4‐diethoxypillar[5]arene subunit, the structure of the compound was confirmed by X‐ray crystal structure analysis. Owing to a good hydrophilic/hydrophobic balance, stable Langmuir films have been obtained for these rotaxanes and the size of the peripheral alkyl chains on the pillar[5]arene subunit has a dramatic influence on the reversibility during compression–decompression cycles. Indeed, when these are small enough, molecular reorganization of the rotaxane by gliding motions are capable of preventing strong π–π interactions between neighboring macrocycles in the thin film.     

Ring and cage compounds from complexes of group 13 metal halides with ethylenediamine: Experiment and theory

Formation of gaseous ring and cage compounds by thermolysis of the complexes between group 13 metal halides MX₃ and ethylenediamine (en) has been observed experimentally by mass spectrometry method (M = Al, Ga; X = Cl, Br, I) and studied theoretically. Existence of gaseous associates with molecular weight of 600-900 amu was observed for all studied systems. The abundance of the high molecular weight species decreases in order AlBr₃ > AlI₃ > GaCl₃ > GaBr₃. For aluminum compounds, formation of carbon-free cubane-type clusters was evidenced. Theoretical ab initio studies at B3LYP/LANL2DZ(d,p) level of theory have been performed for the series of the ring and cage oligomer compounds in Al₂Br₆-en system. A mechanistic pathway of the formation of inorganic rings and cages by subsequent HBr elimination and oligomerization reactions has been proposed. It is concluded that elimination reactions take place in the condensed phase.     

Finite-element formulations of shear localization in granular materials

Displacement and mixed finite element formulations of shear localization in granular materials are presented. The formulations are based on hypoplastic constitutive laws for soils and the mixed-enhanced treatment involving displacement, strain and stress rates as independently varied fields. Included in these formulations are the standard displacement method, the three-field mixed formulation, the method of incompatible modes, the enhanced assumed strain method and the mixed enhanced strain method. Several numerical examples demonstrating the capability and performance of the different finite element formulations are presented. The numerical results are compared with available experimental data of Hostun RF sand and numerical results of Karlsruhe sand on biaxial tests. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)