Theoretical study of dihydrogen bonded clusters of water with tetrahydroborate

Ab initio calculations were used to analyze interactions of BH₄ ^? with 1?C4 molecules of H₂O at the MP2/6-311++G(d,p) and B3LYP/6-311++G(d,p) computational levels. The negative cooperativity for dihydrogen bond clusters containing H₂O···H₂O hydrogen bonds is more remarkable. The negative cooperativity is increased with increasing the size and also the number of hydrogen bonds in the cluster. The B?CH stretching frequencies show blue shifts with respect to cluster formation. Also greater blue shift of stretching frequencies where predicted for B?CH bonds which did not contribute in dihydrogen bonding with water molecules. The structures obtained have been analyzed with the Atoms in Molecules (AIM) methodology.     

A New Complex as a Dimer of a Silver Ion with AMTTO and Phosphane Ligands. The Crystal Structure of {[(AMTTO)Ag(PPh3)2]NO3}2·0.5CH3OH·0.5H2O

Reaction of 4‐amino‐6‐methyl‐1,2,4‐triazine‐3‐thione‐5‐on (AMTTO) as a bidentate ligand with silver nitrate and triphenyl phosphine as the co‐ligand make the centrosymmetric dimeric complex {[(AMTTO)Ag(PPh₃)₂]NO₃}₂·0.5CH₃OH·0.5H₂O ( 1 ). 1 was characterized by elemental analyses, IR‐ and NMR spectroscopy as well as X‐ray diffraction studies. The silver atom in 1 has distorted tetrahedral coordination. 1 crystallizes in triclinic space group . Crystal data for 1 at −80 °C: a = 1185.8(1), b = 1314.6(1), c = 1385.3(1) pm, α = 97.78(1)°, β = 111.38(1)°, γ = 92.41(1)°, Z = 2, R₁ = 0.0377.     

Organocopper-based magnetically recoverable and reusable nanocatalyst for efficient synthesis of novel 1,2,3-triazole-based sulfonamides in green medium

Research on Chemical Intermediates - We report robust green synthesis of novel 1,2,3-triazole-based sulfonamides bearing different motifs such as fluorine under click conditions in presence of a...     

Synthesis of 4H-chromene derivatives by reaction between alkyl isocyanides and dialkyl acetylenedicarboxylate in the presence of 6-hydroxyquinoline

The reactive intermediate generated by the addition of alkyl isocyanides to dialkyi acetyienedicarboxyiate was trapped by 6- quinolinol to produce highlyfunctionalized 4H-chromenes in fairly good yields.     

Multivariate curve resolution-alternating least squares (MCR-ALS) and central composite experimental design for monitoring and optimization of simultaneous removal of some organic dyes

In this work, multivariate curve resolution-alternating least squares (MCR-ALS) has been applied to resolve and study the simultaneous degradation of three toxic organic dyes using Fenton reaction. Second-order kinetic-spectrophotometric data in the simultaneous degradation of malachite green, crystal violet and methylene blue were analyzed by MCR analysis to get their concentration profiles and calculate their degradation factors. The effect of three parameters (Fe²⁺, H₂O₂ concentration and initial pH) and their possible interaction in the simultaneous degradation of mentioned dyes were studied and optimized using experimental design and response surface method. Acquiring second-order data makes possible the analysis and study of the studied dyes in the gray systems which is termed as second-order advantage in the literatures. The prominent point of this work is the combination of second-order data and response surface methodology.     

Improvement of thermal decomposition properties of ammonium perchlorate particles using some polymer coating agents

This research aimed to investigate the optimum conditions for modification of thermal decomposition properties of ammonium perchlorate (AP) particles through microencapsulation techniques. A solvent/non-solvent method has been used to perform microencapsulation of AP particles with some polymer-coating agents such as viton A and nitrocellulose (NC). Differential scanning calorimetry, thermogravimetry, and scanning electron microscopy have been exploited to investigate the thermal properties, heat of decomposition, and coating morphology of pure and coated samples. The preliminary results revealed that AP microparticle could be effectively coated with both NC and viton, but the latter significantly and unfavorably attenuated heat of decomposition of AP so NC was chosen as an appropriate coating agent for modification of thermal properties of AP. The thermal analysis of NC-coated samples, prepared at optimized coating conditions, showed that its first stage decomposition temperature increases about 12 °C with respect to uncoated sample and reaches to 305 °C. Also, the apparent activation energy (E), ΔG ^≠, ΔH ^≠, and ΔS ^≠ of the decomposition processes of the pure and coated AP particles at the optimum conditions were obtained by non-isothermal methods that proposed by ASTM and Ozawa. Finally, the results of this investigation showed that microencapsulation of AP particles with fibrous NC enhance its heat of decomposition (~120 J g^?1) with no obvious effect on kinetic parameters and thermal decomposition temperature.     

Determination of trace amounts of cadmium,copper and nickel in environmental water and food samples using GO/MgO nanocomposite as a new sorbent

A solid phase extraction method based on graphene oxide (GO) modified with magnesium oxide (MgO) nanoparticles was developed for the preconcentration and determination of trace amounts of cadmium, copper and nickel ions. The adsorbed analytes were eluted by 4.0 mL of 0.1 M (EDTA) and injected to flame atomic absorption spectrometer. The factors influencing the complex formation and extraction of these heavy metals were optimized. Studies on potential interference by various anions and cations showed the method to be highly selective. The preconcentration factor was about 11 with relative standard deviation of <4.0 for 8 replication determination. The detection limits for the Cd, Cu, Ni were found to be 0.5, 3.4 and 25 µg L^?1, respectively. The method was successfully applied for the determination of cadmium, copper and nickel in tap water, well water, sea water, rice and macaroni samples with spike recoveries ranging 93–105 %.     

Are Pro<Superscript>8</Superscript>/Pro<Superscript>18</Superscript> really critical for functional dynamic behavior of human endostatin N-terminal peptide? A comparative molecular dynamics study

Endostatin which is derived from the non-collagenous domain 1 of collagen XVIII and is a recently identified broad spectrum anti-angiogenesis agent, inhibits 65 different tumor types. The N-terminal fragment of endostatin protein (ES) has the same antitumor, antimigration and antipermeability effects as the entire protein. In the current study, we modeled two mutant variants of ES with two mutation sites (M1-ES (Pro⁸ → Ala) and M2-ES (Pro¹⁸ → Ala)) and tried to understand proline’s effect on the peptide structure/stability by introducing P⁸A/P¹⁸A mutations, and then in order to gain functional insight into mutation caused by amino acid substitution to the peptide structure/function, these effects were predicted using computational tools. From the RMSD analyses, it can be concluded that dynamic behavior of wild-type and mutant structures was not significantly different from each other and all systems reached equilibrium. The RMSF analysis also revealed that the M2-ES has smaller overall flexibility than the WT-ES and M1-ES structures. The radius of gyration analysis then confirmed the structure of M2-ES compared to wild-type and M1 variant becomes more compact during simulation of our systems. Finally, molecular dynamics simulation analysis shows that replacement of Pro residue with Ala is able to induce a distinct β-sheet in both mutant structures. Indeed, the docking analysis shows the WT-ES and M2-ES bind to the same region of α_vβ₃ integrin, suggesting similar interaction pattern with a relatively equal binding energy into this receptor. Our results speculated that the P⁸A/P¹⁸A replacements confer no improvement (or no tangible weakness) in the peptide biological activity although is able to change structural conformation of N-terminal fragment of human endostatin protein.