Efficient and selective oxidation of alcohols in water employing palladium supported nanomagnetic Fe3O4@hyperbranched polyethylenimine (Fe3O4@HPEI.Pd) as a new organic–inorganic hybrid nanocatalyst

Palladium immobilized magnetic nanoFe₃O₄@hyperbranched polyethylenimine (Fe₃O₄@HPEI.Pd) was prepared according to a simple and cost effective pathway and it was employed as a new efficient and selective organic–inorganic hybrid nanocatalyst for the aqueous oxidation of primary and secondary alcohols to their corresponding products in good yields applying oxone (potassium hydrogen monopersulfate) and H₂O₂ as an oxidant at room temperature. Moreover, the catalytic system was reused at least 13 times without significant loss of activity. The complete characterization of this efficient nanocatalyst was investigated by FTIR, UV–Vis, TEM, SEM, XRD, TGA, VSM, ICP and EDX techniques.     

Facile synthesis of PtSnZn nanosheet thin film at oil–water interface by use of organometallic complexes: An efficient catalyst for methanol oxidation and p‐nitrophenol reduction reactions

PtSnZn nanosheet thin film with stable and high activity towards methanol electro‐oxidation was synthesized via a simple reduction of organometallic precursors including [PtCl₂(cod)] (cod = cis,cis‐1,5‐cyclooctadiene) and [Sn(CH₃)₄] complexes, in the presence of [Zn(acac)₂] (acac = acetylacetonate) complex at toluene–water interface. Catalytic activities of PtSnZn nanosheets were investigated in the p‐nitrophenol (p‐Nip) reduction and methanol oxidation reactions. The obtained results demonstrate that PtSnZn nanosheets exhibit a good electrocatalytic performance for methanol oxidation reaction, the catalytic activity of the PtSnZn nanosheets being at least 3.5 times higher than that of Pt nanoparticle thin film. Also, the apparent rate constant obtained for p‐Nip reduction with the PtSnZn nanosheets is at least 2.3 times higher than that for Pt nanoparticle thin film due to the appropriate interaction between platinum, tin and zinc metals and geometric properties of PtSnZn nanosheet thin film. Nanosheets are highly favourable for superior catalytic performances due to their geometric properties. A facile and efficient route was used to synthesize trimetallic alloy thin film at oil–water interface.     

Efficient one‐pot synthesis of disubstituted 1,3,4‐oxadiazole derivatives from the reaction of (N‐isocyanimino)triphenylphosphorane,acetaldehyde, a secondary amine,and an electron‐poor (E)‐cinnamic acid

The iminium intermediate formed by the reaction of a secondary amine with acetaldehyde was reacted by (N‐isocyanimino) triphenylphosphorane in the presence of an electron‐poor (E)‐cinnamic acid derivative to give the corresponding iminophosphorane intermediate, whose intramolecular the aza‐Wittig reaction led to disubstituted 1,3,4‐oxadiazole derivatives. The reactions were completed under neutral conditions at room temperature, and the corresponding disubstituted 1,3,4‐oxadiazole derivatives were produced in excellent yields. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 22:79–84, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20660     

Kinetic,Equilibrium and Isotherm Studies of Cadmium Removal from Aqueous Solutions by Oxidized Multi‐Walled Carbon Nanotubes and the Functionalized Ones with Thiosemicarbazide and Their Toxicity Investigations: A Comparison

The multi‐walled carbon nanotubes (MWCNTs) were first oxidized by nitric acid to form a MWCNT‐COOH. Then, it was modified with thiosemicarbazide to produce MWCNT‐semi. Thus, these carbon materials, MWCNTs, MWCNT‐COOH and MWCNT‐semi, have been used as efficient adsorbents for the removal of cadmium from aqueous solutions. The influence of variables including pH, concentration of the cadmium, amount of adsorbents and contact time was investigated by the batch method. The kinetic studies carried out using different kinetic models such as pseudo‐first‐order, pseudo‐second‐order, and intraparticle diffusion models. The sorption process with each adsorbent was well described by pseudo‐second‐order kinetics which it was agreed well with the experimental data. The values of regression coefficient of various adsorption isotherms like Langmuir, Freundlich and Tempkin to obtain the characteristic parameters of each model have been carried out. The results showed which the Langmuir isotherm for all adsorbents and Tempkin model for MWCNT‐COOH and MWCNT‐semi was found to best represent the measured sorption data. Toxicity of these samples was evaluated in human embryonic kidney HEK293 and human breast cancer SKBR3 cell lines after culturing cells for 24 h. Cellular investigations showed that the modified MWCNTs in particular MWCNT‐semi have considerably significant toxic impact on SKBR3 as compared to HEK293 at concentration 3 µg/mL.     

Synthesis of new nanocopolymer containing β-lactams

Several new monocyclic β-lactam monomers bearing the NO₂ group 2a–g were synthesized via a [2 + 2] ketene–imine cycloaddition reaction (Staudinger reaction). Calculation of coupling constant of H-3 and H-4, and the X-ray crystallography of β-lactam 2e confirmed the cis stereochemistry of these β-lactams. Then aminophenyl β-lactams were synthesized by the reduction of NO₂ to NH₂ group in the presence of Raney Ni and hydrazine hydrate. Treatment of these aminophenyl β-lactams with acryloyl chloride and sodium bicarbonate (NaHCO₃), afforded the monomers bearing the NHCOCH=CH₂ group. These acrylated β-lactam monomers were dissolved in a warm mixture of butyl acrylate and styrene and then were converted to the corresponding polyacrylate nano β-lactams by emulsion polymerization in water. A unique feature of this methodology is the ability to incorporate water-insoluble compounds directly into the nanoparticle framework. Structures of the synthesized compounds were confirmed by physical and spectral analyses. Dynamic light scattering analysis and transmission electron microscopy of the final emulsions show that the nanoparticles were about 50–70 nm in diameter.     

Synthesis of new polyaryl-substituted imidazoles bridged on enamine or urea moieties and evaluation of their optical and electrochemical properties

Research on Chemical Intermediates - The reaction of the free amine group in polyaryl-substituted imidazole structures with phenyl isocyanate or dimethyl acetylenedicarboxylate gave two new series...     

A method for protein accessibility prediction based on residue types and conformational states

Prediction of protein accessibility from sequence, as prediction of protein secondary structure is an intermediate step for predicting structures and consequently functions of proteins. Most of the currently used methods are based on single residue prediction, either by statistical means or evolutionary information, and accessibility state of central residue in a window predicted. By expansion of databases of proteins with known 3D structures, we extracted information of pairwise residue types and conformational states of pairs simultaneously. For solving the problem of ambiguity in state prediction by one residue window sliding, we used dynamic programming algorithm to find the path with maximum score. The three state overall per-residue accuracy, Q₃, of this method in a Jackknife test with dataset of known proteins is more than 65% which is an improvement on results of methods based on evolutionary information.     

Ziegler‐Natta/Metallocene Hybrid Catalyst for Ethylene Polymerization

A Ziegler‐Natta/metallocene hybrid catalyst was produced and utilized in the polymerization of ethylene with the aim of producing bimodal polyethylene. The MgCl₂ adduct was prepared by a melt quenching method and Cp₂ZrCl₂ and TiCl₄ catalysts were loaded, respectively, after treating the surface with TiBAl. The polymerization kinetics involved an induction period, followed by fragmentation and expansion of particles. SEM micrographs revealed that the spherical morphology was retained through the initial mild reaction conditions of induction period. The polymers produced showed bimodal molecular weight distribution patterns, suggesting that both components of the hybrid catalyst were active over the support.

     

A Concise Review of Current In Vitro Chemical and Cell-Based Antioxidant Assay Methods

Antioxidants remain interesting molecules of choice for suppression of the toxic effects of free radicals in foods and human systems. The current practice involves the use of mainly synthetic molecules as potent antioxidant agents. However, due to the potential negative impact on human health, there is an intensive effort within the research community to develop natural alternatives with similar antioxidant efficacy but without the negative side effects of synthetic molecules. Still, the successful development of new molecules depends on the use of reliable chemical or cell culture assays to screen antioxidant properties. Chemical antioxidant assays include the determination of scavenging ability against free radicals such as DPPH, superoxide anion radicals, hydroxyl radicals, hydrogen peroxide, and nitric oxide. Other antioxidant tests include the ability of compounds to bind and sequester prooxidant metal cations, reduce ferric iron, and attenuate the rate of lipid oxidation. Ex vivo tests utilize cell cultures to confirm entry of the molecules into cells and the ability to quench synthetic intracellular free radicals or to stimulate the increased biosynthesis of endogenous antioxidants. In order to assist researchers in their choice of antioxidant evaluation methods, this review presents background scientific information on some of the most commonly used antioxidant assays with a comparative discussion of the relevance of published literature data to food science and human nutrition applications.