The effect of electron withdrawing croups on the stability of thiabenzenes

The reactions of p-trifluoromethylphenyllithium with 2,4,6-triarylthiopyrylium perehlorates (Ar = Ph, p-CH₃OC₆H₄, p-NMe₂C₆H₄) have been studied. The initially formed thiabenzenes were not slable enough to he isolated and rearranged readily to their corresponding 4-(p-tri-fluoromethylphenyl)-2,4,6-triarylthiopyrans. The instability of the intermediate thiabenzenes reveals that, in contrast to the stabilization effect of the electron-withdrawing p-chloro- and pentalluorophcnyl groups attached to carbon atoms in sulfur ring, the electron-withdrawing p-lrilluoromethyl group on subsliluenls attached to sulfur decreases the stability of thiabenzenes.     

Square-wave voltammetric (SWV) determination of Captopril in reconstituted serum and pharmaceutical formulations

A simple, fast and sensitive square-wave voltammetric (SWV) method for the determination of trace amounts of Captopril in pharmaceutical formulation and reconstituted serum is reported. A three-electrode system containing the static mercury drop electrode (SMDE) working electrode, Pt auxiliary electrode and Ag/AgCl reference electrode was used throughout. Sodium sulfite was used as both supporting electrolyte and oxygen removing agent. No nitrogen purging is needed for oxygen removal from sample solution. Calibration graph showed good linearity in the concentration range of 0.5-50.0 μg mL⁻¹ of Captopril and regression coefficient of 0.9957 is obtained. R.S.D. for eight replicate measurements and LOD of the proposed method are 1.2% and 6.28 × 10⁻³ μg mL⁻¹, respectively. The effect of various parameters (equilibration time, scan increment, pulse height, drop size, frequency and sodium sulfite concentration) on the determination were investigated. The procedure was successfully applied to the determination of Captopril in pharmaceutical formulation and reconstituted serum.     

Simulation on the Effect of Brownian Motion on Nanoparticle Trajectories in a Pulsed Microplasma Cluster Source

We describe a simulation of the nanoparticle trajectories in a pulsed cluster beam source. Clusters, formed by condensation of atomic vapor in a helium bath, and considered here as rigid spheres having a diameter of 1.5nm, were tracked during their travel inside the source cavity, an aerodynamic lens, and a cylindrical nozzle. Steady state supersonic laminar flow of helium is considered in an axi-symmetric geometry aiming to simulate, within some limitations, the conditions under which cluster formation takes place in a pulsed microplasma cluster source. In spite of the unsteady nature of the pulsed source, the time scale characterizing particle motion in the flow field is significantly smaller than the characteristic time constant for the evolution of gas pressure in the source. For this reason, a steady simulation can shed some light on the understanding of processes governing nanoparticle motion in a pulsed vaporization source. The extent to which the Brownian diffusion can affect the particle extraction from the source is investigated. Simulations have shown that the Brownian motion perturbs the clusters from the trajectories dictated by the carrier gas and increases the rate of cluster deposition on the source internal walls. However, it does not hinder the aerodynamic focalization produced by the lens even in nano-size cluster regime. This result is qualitatively confirmed by experiment.     

The effect of the chemical composition and the volume of coated carbonate calcium on epoxy paint properties

Russian Journal of Applied Chemistry - Titanium dioxide (TiO2) is widely used in the paint industry as a white pigment. To reduce the high cost of TiO2, mineral fillers such as different calcites...     

Cloning and Expression of Che a 1, the Major Allergen of <Emphasis Type="Italic">Chenopodium album</Emphasis> in <Emphasis Type="Italic">Escherichia coli</Emphasis>

Chenopodium album is a weedy annual plant in the genus Chenopodium. C. album pollen represents a predominant allergen source in Iran. The main C. album pollen allergens have been described as Che a 1, Che a 2, and Che a 3. The aim of this work was to clone the Che a 1 in Escherichia coli to establish a system for overproduction of the recombinant Che a 1 (rChe a 1). In order to clone this allergen, the pollens were subjected to RNA extraction. A full-length fragment encoding Che a 1 was prepared by polymerase chain reaction amplification of the first-strand cDNA synthesized from extracted RNA. Cloning was carried out by inserting the cDNA into the pET21b (+) vector, thereafter the construct was transformed into E. coli Top10 cells and expression of the protein was induced by IPTG. The rChe a 1 was purified using histidine tag in recombinant protein by means of Ni–NTA affinity chromatography. IgE immunoblotting, ELISA, and inhibition ELISA were done to evaluate IgE binding of the purified protein. In conclusion, the cDNA for the major allergen of the C. album pollen, Che a 1, was successfully cloned and rChe a 1 was purified. Inhibition assays demonstrated allergic subjects sera reacted with rChe a 1 similar to natural Che a 1 in crude extract of C. album pollen. This study is the first report of using the E. coli as a prokaryotic system for Che a 1 cloning and production of rChe a 1.     

Synthesis of new 4(3H)-quinazolinone derivatives using 5(4H)-oxazolones

New derivatives of 5(4H)-quinazolinone containing 2-imidazolin-5-one rings have been prepared from 5(4H)-oxazolone derivatives.     

Effects of electron‐withdrawing group on the photoisomerization of tetraaryl‐4H‐thiopyran‐1,1‐dioxides

Syntheses and photoisomerization of the new sulfone derivatives, 4,4‐di (p‐trifluoromethylphenyl)‐2,6‐diphenyl‐4H‐thiopyran‐1, 1‐dioxide and 4‐(p‐trifluoromethylphenyl)‐2,4,6‐triphenyl‐4H‐thiopyran‐1,1‐dioxide, have been investigated. The relative molar ratios of the photoproducts are compared with those of 2,4,4,6‐tetraphenyl‐4H‐thiopyran‐1,1‐dioxide as well as electron‐donating substituted 4‐methyl‐2,4,6‐triaryl‐4H‐thiopyran‐1,1‐dioxides as model compounds under identical experimental conditions using ¹H NMR spectroscopy. The results observed are discussed on the basis of a triplet excited state di‐π‐methane rearrangement. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:557–561, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20455