Selective Acetylation of Alcohols and Amines with Ethyl Acetate in the Presence of H<Subscript>6</Subscript>[PMo<Subscript>9</Subscript>V<Subscript>3</Subscript>O<Subscript>40</Subscript>] as the Catalyst

Summary. Acetylation of various alcohols and benzyl amine was tested in the presence of H₆[PMo₉V₃O₄₀], a mixed addenda heteropolyacid, in ethyl acetate under reflux condition. Phenols and anilines are not affected under the reaction conditions. Selective transestrification of alcohols can be achieved in the presence of phenol and aniline derivatives using this method.     

Lipid-protein interactions in membranes: effect of lipid composition on mobility of spin-labeled cysteine residues in yeast plasma membrane.

In order to gain direct evidence for lipid-dependent protein conformation in membrane, effects of modification of lipid composition on mobility of spin-labeled cysteine residues were investigated in the plasma membrane of the yeast Saccharomyces cerevisiae. Conversion of the bulk of phospholipids to diglycerides by treatment of the membrane with phospholipase C substantially enhanced spectral anisotropy. However, alterations of the viscosity of the lipid-bilayer by enriching the membrane with palmitelaidic or oleic acid had no effect on mobility of spin-labeled cysteine residues. These observations indicate that while the spin-labeled residues are not in direct contact with the lipid core of the membrane, there are lipid-protein interactions to the extent that removal of the polar portion of the bulk of phospholipids induces conformational changes in proteins, which in turn restrict mobility of these residues. It is concluded that conformation of membrane proteins on lipid structure and that phospholipids have a role in preserving the native conformation of proteins.     

Flutter,limit cycle oscillation,bifurcation and stability regions of an airfoil with discontinuous freeplay nonlinearity

Nonlinear Dynamics - This paper is devoted to study a two-dimensional airfoil oscillating in pitch and plunge degrees of freedom. A nonlinear analysis is performed to investigate the effects of a...     

Surface modified SPIONs‐Cr(VI) ions‐immobilized organic‐inorganic hybrid as a magnetically recyclable nanocatalyst for rapid synthesis of polyhydroquinolines under solvent‐free conditions at room temperature

In this work, a magnetic hybrid dichromate nanocomposite with triphenylphosphine surface modified superparamagnetic iron oxide nanoparticles (SPIONs) as a recyclable nanocatalyst was designed, prepared and characterized by Fourier transform infrared spectroscopy (FT‐IR) spectra, X‐ray diffraction (XRD) pattern analysis, vibrating sample magnetometer (VSM) curves, X‐ray fluorescence (XRF) analysis, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images and dynamic light scattering (DLS) analysis. Then, it was used in a green and efficient procedure for one‐pot multicomponent synthesis of polyhydroquinoline derivatives by the condensation of aldehydes, dimedone or 1,3‐cyclohexadione, ethyl acetoacetate and ammonium acetate. This protocol includes some new and exceptional advantages such as short reaction times, low catalyst loading, high yields, solvent‐free and room temperature conditions, easy separation and reusability of the catalyst.     

Decorations of graphene oxide with cisplatin toward investigation of fluorescence quencher on regulatory sequence of BRCA1 and BRCA2

Journal of the Iranian Chemical Society - Herein, we investigated the interaction of cisplatin loaded on GO (GO@CDDP) with two regulatory sequences, BRCA1 and BRCA2, synthesized from ssDNA based on...     

Assessment of nanocomposites based on unsaturated polyester resin/nanoclay under impact loading

The aim of this study is to investigate the performance of nanoclay reinforced unsaturated polyester (UP) resin under impact loads. Nanocomposite specimens containing nanoclay in 0, 1.5, and 3 (wt%) were prepared by melt mixing method. X‐ray diffraction, transmission electron microscopy analysis, scanning electron microscope photographs, and viscosity changes in liquid state resin confirmed exfoliation and intercalation of the nanoclay in the UP resin system used. Tensile modulus showed an increase with increase in nanoclay content. However, the tensile strength and elongation at break exhibited reducing performance with increase in nanoclay content. Izod impact test results indicated better performance for the specimens containing nanoclay reinforcements, with 1.5 (wt%) of nanoclay specimens showing the highest value. High velocity impact tests were carried out using gas gun in velocity range of 20–100 m/sec and harden steel hemispherical tip projectile with diameter of 8.7 mm and weight of 11.54 g. Results for high velocity impact test indicated better performance by the specimens containing nanoclay, with 1.5 (wt%) nanoclay showing the highest attained value. Damage assessments of impact area for all specimens showed spalling type brittle failure with punch out and sever fragmentation pattern. Copyright © 2011 John Wiley & Sons, Ltd.     

Facile synthesis of α-hydroxy carboxylic acids from the corresponding α-amino acids

An effective and improved procedure is developed for the synthesis of α-hydroxy carboxylic acids by treatment of the corresponding protonated α-amino acid with tert-butyl nitrite in 1,4-dioxane–water. The amino moiety must be protonated and located α to a carboxylic acid function in order to undergo initial diazotization and successive hydroxylation, since neither β-amino acids nor acid derivatives such as esters and amides undergo hydroxylations. The method is successfully applied for the synthesis of 18 proteinogenic amino acids.     

A simple and clean method for multicomponent synthesis of spiro [indole-tetrahydropyrano(2,3-d)pyrimidine] derivatives using SBA-Pr-SO3H as catalyst under solvent-free conditions

Sulfonic acid functionalized SBA-15 (SBA-Pr-SO₃H) as a new nanoporous solid acid catalyst was applied in the green one-pot synthesis of spiro[indole-tetrahydropyrano(2,3-d)pyrimidine] derivatives via three-component reaction of isatins, malononitrile or cyanoacetic esters and barbituric acids under solvent-free conditions. SBA-Pr-SO₃H was proved to be an efficient heterogeneous nanoporous solid acid catalyst with a pore size of 6 nm, which could be easily handled and removed from the reaction mixture by simple filtration and can be recovered and reused several times without any loss of activity. The advantages of this methodology are high product yields, being environmentally benign, short reaction times, and easy handling.