Porous triazine polymer: A novel catalyst for the three-component reaction

A new porous triazine-based covalent organic polymer (Triazine-COP) was prepared through the Schiff-base condensation of 2,4,6-tris(4-formyl phenoxy)-1,3,5-triazine and 4,4′-oxydianiline, under sonication. The synthesized Triazine-COP with a high surface area was stable in water and other organic solvents. In the next step, Au (III) ions were immobilized on the nitrogen-rich Triazine-COP that on the reduction with NaBH₄ produced the heterogeneous catalyst of gold clusters in nanosize (Au-NCs@Triazine-COPs). It was applied as an efficient catalyst for the A³ coupling reaction of alkynes, aldehydes with and amines. Both electron-withdrawing/releasing groups produced the corresponding propargylamines with high yields. The high activity of the Au-NCs@Triazine-COPs in this reaction was because of the nanoporous structure of the support that enables the high dispersion and an unhindered open environment for the NCs. The catalyst was reused up to 7 times without significant loss in activity.     

Asymmetric deformation density analysis in carbon nanotubes

Electrons and holes as charge carriers appear when a molecular system is exposed to external electric field. For nonsymmetric molecules, the distribution of charge carriers is also nonsymmetric. Although symmetric distribution of charge carriers is expected when the molecular system is symmetric, as the present work shows, they are not symmetric unexpectedly; that is, electrons and holes are not each other's mirror images. In this respect, asymmetric deformation density analysis is introduced to measure the extent of asymmetric distribution of electrons and holes as charge carriers when the symmetric system is exposed to symmetric external potential. Segments of (5,0) carbon nanotubes with different lengths are selected as symmetric systems, and a linear electric field is applied along the principal axis as symmetric potential. Results show that, at high electric fields, electrons tend to localize at the ends, while holes tend to occupy the middle area of carbon nanotube segments. While charge carriers play a vital role in molecular conductivity, asymmetric distribution of electrons and holes in symmetric systems has not yet been reported.     

Screening of allelopathic trees for their antifungal potential against Alternaria alternata strains isolated from dying-back Eucalyptus spp

Antifungal activity of methanolic extracts of leaves of three tree species, namely Azadirachta indica L., Syzygium cumini (L.) Skeels. and Melia azedarach L. was evaluated against two strains of Alternaria alternata, isolated from dying-back trees of two Eucalyptus spp., namely Eucalyptus citriodora and Eucalyptus globulus. All the concentrations (1,?2,?…?,?5% w/v) of the methanolic extracts of the three tree species significantly reduced the fungal biomass. There were reductions in the ranges 82-88%, 88-96% and 83-96% in the biomass of A. alternata strains due to different concentrations of the leaf extracts of S. cumini, A. indica and M. azedarach, respectively. Methanolic extract of M. azedarach was subjected to further fractionation using n-hexane, chloroform, ethyl acetate and n-butanol successively in the order of increasing polarity. Aqueous and n-butanol fractions gave promising results in the significant decrease in fungal biomass. This study concludes that aqueous and n-butanol fractions of methanolic leaf extract of M. azedarach can be used as biofungicides for the management of A. alternata.     

Volatile constituent distribution of Prangos coryombosa Boiss at two stages of growth

The volatile constituents obtained by hydrodistillation of the aerial parts of Prangos coryombosa at the vegetative and flowering stages were analysed by GC and GC-MS. Twenty-one and 28 compounds were identified from the oils obtained from the plant's aerial parts at the vegetative and flowering stages, respectively. The oil from the vegetative stage was dominated by β-elemene (22%) and spathulenol (12.5%), whereas the oil from the flowering period was characterised by β-elemene (40.7%) and kessane (10.7%). The main compounds of the oil at the flowering stage were isolated by TLC and their structures were elucidated by (1)H and (13)C NMR. The results have ecological and taxonomical significance.     

Application of desymmetrization protocol for the formal total synthesis of emericellamide B

A highly convergent formal total synthesis of emericellamide B, a 19-membered antibacterial depsipeptide is described. The key feature of the strategy is the generation of four stereogenic centers from a bicyclic precursor via desymmetrization technique and utilization for emericellamide B and related natural product synthesis.     

Simultaneous determination of 2‐arachidonoylglycerol, 1‐arachidonoylglycerol and arachidonic acid in mouse brain tissue using liquid chromatography/tandem mass spectrometry

Endocannabinoids (ECs), such as anandamide (AEA) and 2‐arachidonoylglycerol (2‐AG), modulate a number of physiological processes, including pain, appetite and emotional state. Levels of ECs are tightly controlled by enzymatic biosynthesis and degradation in vivo. However, there is limited knowledge about the enzymes that terminate signaling of the major brain EC, 2‐AG. Identification and quantification of 2‐AG, 1‐AG and arachidonic acid (AA) is important for studying the enzymatic hydrolysis of 2‐AG. We have developed a sensitive and specific quantification method for simultaneous determination of 2‐AG, 1‐AG and AA from mouse brain and adipose tissues by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using a simple brain sample preparation method. The separations were carried out based on reversed phase chromatography. Optimization of electrospray ionization conditions established the limits of detection (S/N = 3) at 50, 25 and 65 fmol for 2‐AG, 1‐AG and AA, respectively. The methods were selective, precise (%R.S.D. < 10%) and sensitive over a range of 0.02–20, 0.01–10 and 0.05–50 ng/mg tissue for 2‐AG, 1‐AG and AA, respectively. The quantification method was validated with consideration of the matrix effects and the mass spectrometry (MS) responses of the analytes and the deuterium labeled internal standard (IS). The developed methods were applied to study the hydrolysis of 2‐AG from mouse brain extracts containing membrane bound monoacylglycerol lipase (MAGL), and to measure the basal levels of 2‐AG, 1‐AG and AA in mouse brain and adipose tissues. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterization of HypoGel-supported Pd nanocatalysts for Suzuki reaction under mild conditions

A new heterogeneous catalyst composed of Pd nanoparticles immobilized within a HypoGel resin has been prepared in the absence of any ligands using an extensive cross-linking method. This new-ly develop...     

Pentafluorophenylammonium triflate as a suitable and effective metal-free catalyst for the synthesis of quinazoline derivatives via one-pot multicomponent method

Research on Chemical Intermediates - A simple and facile synthesis of highly functionalized quinazoline derivatives has been successfully developed by treatment of aldehydes, ammonium acetate, and...     

p-sulfonic acid calix[4]arene: An efficient reusable organocatalyst for the synthesis of bis(indolyl)methanes derivatives in water and under solvent-free conditions

In this work, a green, simple and highly efficient procedure for the synthesis of bis(indolyl)methanes is described. The condensation of indoles catalyzed by p-sulfonic acid calix[4]arene in water and under solvent-free conditions afford the title compounds in high yields and relatively short reaction times.     

Biosurface engineering through ink jet printing

The feasibility of thermal ink jet printing as a robust process for biosurface engineering was demonstrated. The strategy investigated was to reconstruct a commercial printer and take advantage of its colour management interface. High printing resolution was achieved by formulating bio-inks of viscosity and surface tension similar to those of commercial inks. Protein and enzyme denaturation during thermal ink jet printing was shown to be insignificant. This is because the time spent by the biomolecules in the heating zone of the printer is negligible; in addition, the air and substrate of high heat capacity absorb any residual heat from the droplet.Gradients of trophic/tropic factors can serve as driving force for cell growth or migration for tissue regeneration. Concentration gradients of proteins were printed on scaffolds to show the capability of ink jet printing. The printed proteins did not desorb upon prolonged immersion in aqueous solutions, thus allowing printed scaffold to be used under in vitro and in vivo conditions. Our group portrait was ink jet printed with a protein on paper, illustrating that complex biopatterns can be printed on large area. Finally, patterns of enzymes were ink jet printed within the detection and reaction zones of a paper diagnostic.