A three-component cyclocondensation reaction for the synthesis of new triazolo[1,5-a]pyrimidine scaffolds using 3-aminotriazole,aldehydes and ketene N,S-acetal

Molecular Diversity - This study describes the use of 3-aminotriazole, different aldehydes and N-methyl-1-(methylthio)-2-nitroethenamine as a ketene N,S-acetal in a three-component condensation for...     

Spectrophotometric resolution of ternary mixtures of pseudoephedrine hydrochloride, dextromethorphan hydrobromide, and sodium benzoate in syrups using wavelength selection by net analyte signals calculated with hybrid linear analysis

Hybrid linear analysis (HLA), as a recent factor-based multivariate calibration technique, was applied for the spectrophotometric determination of ternary mixtures of pseudoephedrine hydrochloride (PSU), dextromethorphan hydrobromide (DXT), and sodium benzoate (BNZ). The utilized HLA was assisted by a wavelength selection procedure which was based on the calculation of the net analyte signal (NAS) regression plot in any considered wavelengths window for each test sample, in addition to a moving window strategy for searching the region with maximum linearity of NAS regression plot (minimum error indicator (EI)). HLA was applied because it was simpler to adapt to the NAS regression plot methodology, and also used less factors than partial least squares (PLS). An orthogonal array design was applied for formation of calibration and prediction sets in the concentration ranges 0-7500 μmol L⁻¹ for PSU, 0-300 μmol L⁻¹ for DXT, and 0-1400 μmol L⁻¹ for BNZ. The method had the ability to select wavelength regions that minimize the effect of non-linearity of the spectral data, in addition to that of non-modeled interferences. The application of the selected wavelength regions improved the obtained relative standard error of predictions for PSU, DXT, and BNZ, respectively, from 5.24, 8.67, and 5.48% to 2.19, 5.21, and 3.62% (using lower number of factors). To check the ability of the proposed method in selection of linear regions of spectra, a test for detecting non-linear regions of spectral data in multivariate spectroscopic assays was also described. Additives in the commercial syrup samples did not interfere with their determinations. The method was successfully applied for the determination of pseudoephedrine HCl, dextromethorphan HBr, and sodium benzoate in cough suppressant syrup samples.     

A review on experimental studies of surfactant adsorption at the hydrophilic solid-water interface

The progresses of understanding of the surfactant adsorption at the hydrophilic solid-liquid interface from extensive experimental studies are reviewed here. In this respect the kinetic and equilibrium studies involves anionic, cationic, non-ionic and mixed surfactants at the solid surface from the solution. Kinetics and equilibrium adsorption of surfactants at the solid-liquid interface depend on the nature of surfactants and the nature of the solid surface. Studies have been reported on adsorption kinetics at the solid-liquid interface primarily on the adsorption of non-ionic surfactant on silica and limited studies on cationic surfactant on silica and anionic surfactant on cotton and cellulose. The typical isotherm of surfactants in general, can be subdivided into four regions. Four-regime isotherm was mainly observed for adsorption of ionic surfactant on oppositely charged solid surface and adsorption of non-ionic surfactant on silica surface. Region IV of the adsorption isotherm is commonly a plateau region above the CMC, it may also show a maximum above the CMC. Isotherms of four different regions are discussed in detail. Influences of different parameters such as molecular structure, temperature, salt concentration that are very important in surfactant adsorption are reviewed here. Atomic force microscopy study of different surfactants show the self-assembly and mechanism of adsorption at the solid-liquid interface. Adsorption behaviour and mechanism of different mixed surfactant systems such as anionic-cationic, anionic-non-ionic and cationic-non-ionic are reviewed. Mixture of surface-active materials can show synergistic interactions, which can be manifested as enhanced surface activity, spreading, foaming, detergency and many other phenomena.     

Characterization and reactivity study of non-heme high-valent iron–hydroxo complexes

A terminal Fe^IIIOH complex, [Fe^III(L)(OH)]²⁻ (1), has been synthesized and structurally characterized (H₄L = 1,2-bis(2-hydroxy-2-methylpropanamido)benzene). The oxidation reaction of 1 with one equiv. of tris(4-bromophenyl)ammoniumyl hexachloroantimonate (TBAH) or ceric ammonium nitrate (CAN) in acetonitrile at −45 °C results in the formation of a Fe^IIIOH ligand radical complex, [Fe^III(L˙)(OH)]⁻ (2), which is hereby characterized by UV-visible, ¹H nuclear magnetic resonance, electron paramagnetic resonance, and X-ray absorption spectroscopy techniques. The reaction of 2 with a triphenylcarbon radical further gives triphenylmethanol and mimics the so-called oxygen rebound step of Cpd II of cytochrome P450. Furthermore, the reaction of 2 was explored with different 4-substituted-2,6-di-tert-butylphenols. Based on kinetic analysis, a hydrogen atom transfer (HAT) mechanism has been established. A pK_a value of 19.3 and a BDFE value of 78.2 kcal/mol have been estimated for complex 2.

One-electron oxidation of an Fe^III–OH complex (1) results in the formation of a Fe^III–OH ligand radical complex (2). Its reaction with (C₆H₅)₃C˙ results in the formation of (C₆H₅)₃COH, which is a functional mimic of compound II of cytochrome P450.     

Functionalization of cellulose nanocrystal powder by non-thermal atmospheric-pressure plasmas

Cellulose - Despite promising characteristics such as the biodegradability and the environmentally benign nature of cellulose nanocrystal (CNC) based composites, their poor dispersion and...     

Nonspecific Effect of Double-Stranded (ds) RNA on Prophenoloxidase (proPO) Expression in Penaeus monodo n

RNA interference-mediated silencing is an effective way of controlling white spot syndrome virus (WSSV). However, the effect of RNAi on the innate immune mechanism is not well understood. Prophenoloxidase (proPO) is an important component of the shrimp innate immunity. In the present study, nonspecific effect of two double-stranded (ds)RNA-expressing constructs, one targeting vp28 gene of WSSV (pCMV-VP28-LH) and another targeting green fluorescent protein (GFP) (pCMV-GFP-LH) on proPO2 gene expression, is investigated. mRNA expression levels of proPO2 in hemocytes of DNA construct-injected shrimp were estimated using real-time PCR with elongation factor 1-α as internal control. Empty vector (pcDNA)-injected shrimp were used as experimental control. In pCMV-VP28-LH-injected shrimp, proPO2 showed significant upregulation until 48 h post-injection (p.i.). Similarly, pCMV-GFP-LH-injected animals showed high levels of expression until 72 h p.i. WSSV-challenged animals, compared to pcDNA-injected control group, showed no significant change in expression of the gene until 24 h. However, an increased expression was noticed at 48 h p.i. Our results suggest that neither the plasmids nor the long hairpin RNA expressed by the constructs has any nonspecific silencing effect on the proPO2 expression. On the contrary, the consistent upregulation of proPO2 observed in shrimp injected with dsRNA at early time-points indicates the possibility of nonspecific protection against WSSV infection.     

A new approach in modeling of constant temperature boundary condition in thermal lattice‐Boltzmann method

The lattice‐Boltzmann method is being applied to a diversity of fluid flow and heat transfer problems nowadays. Because of its microscale nature, strict attention should be paid when introducing macroscopic inputs to the model. One of the challenging issues dealing with macroscale and microscale treatment is the implementation of boundary conditions. In this regard constant‐temperature boundaries are frequently used in energy transfer problems. Such boundaries are simply modeled in Navier–Stokes based solvers, but they are not so harnessed in lattice‐Boltzmann models. One of the problems is that the calculated tangential heat flux is not zero along such boundaries in most of the previous models. In the present paper, a model has been developed, which has the capability of controlling tangential heat flux along the constant‐temperature boundaries. It aims to set the heat flux nearly zero along the boundary in midplane grid schemes. Copyright © 2012 John Wiley & Sons, Ltd.     

Finely dispersed palladium on silk‐fibroin as an efficient and ligand‐free catalyst for Heck cross‐coupling reaction

A palladium–fibroin complex (Pd/Fib.) was prepared by the addition of sonicated fibroin fiber in water to palladium acetate solution. Pd (OAc)₂ was absorbed by fibroin and reduced with NaBH₄ at room temperature to the Pd(0) nanoparticles. Powder‐X‐ray diffraction, scanning electron microscopy–energy‐dispersive X‐ray spectroscopy, Fourier transform‐infrared, CHN elemental analysis and inductively coupled plasma‐atomic emission spectroscopy were carried out to characterize the Pd/Fib. catalyst. Catalytic activity of this finely dispersed palladium was examined in the Heck coupling reaction. The catalytic coupling of aryl halides (‐Cl, ‐Br, ‐I) and olefins led to the formation of the corresponding coupled products in moderate to high yields under air atmosphere. A variety of substrates, including electron‐rich and electron‐poor aryl halides, were converted smoothly to the targeted products in simple procedure. Heterogeneous supported Pd catalyst can be recycled and reused several times.     

Ag3[PMo12O40]: An efficient and green catalyst for the synthesis of highly functionalized pyran‐annulated heterocycles via multicomponent reaction

A facile, efficient and eco‐friendly catalytic protocol was developed for the synthesis of medicinally important pyran‐annulated heterocycles via multicomponent reaction (MCR). Cyclocondensation of differently substituted aromatic aldehydes, malononitrile/ethyl cyanoacetate and various β‐dicarbonyl compounds in the presence of Ag₃[PMo₁₂O₄₀]?nH₂O as heterogeneous catalyst, in EtOH–H₂O, afforded diverse pyran‐fused chromene analogues. The merits observed for this approach were it being conducted via MCR, using commercially available or easily accessible starting materials in the presence of a green and easily separable heterogeneous and reusable catalyst, and affording high yields of desired products in very short reaction times with high purity in one‐pot fashion, thus providing a superior alternative approach for the synthesis of pyran‐annulated heterocycles.