Commercially available 5'-DMT phosphoramidites as reagents for the synthesis of vinylphosphonate-linked oligonucleic acids

[reaction: see text]. Commercially available cyanoethyl phosphoramidites derived from T, d(C), d(A), and d(G) were hydrolyzed (1H-tetrazole, MeCN/H2O) to give the corresponding H-phosphonates in excellent yields. Palladium(0)-catalyzed cross-coupling of each of these with the thymidine-derived vinylbromide 2 afforded the corresponding vinylphosphonate-linked dimers TT, d(C)T, d(A)T, and d(G)T in modest to good yields. The TT dimer was further elaborated to give a 5'-DMT-TT-3'-CEP building block, and this was used in the automated synthesis of the TpTTpT tetramer.     

Adsorption of Some Essential Amino Acids on Hydroxyapatite

Samples of synthetic hydroxyapatite, Ca(10)(PO(4))(6)(OH)(2), obtained by wet method and calcined at 1173 K in air were used in an adsorption study of some essential amino acids, mainly histidine, methionine, and tryptophan. Adsorption isotherms were obtained using aqueous solutions of concentration range 2.7x10(-2)-1.3x10(-3) M at 303, 318, and 343 K, under near neutral conditions. The mode of adsorption was studied using IR spectroscopy. The results are discussed in terms of the dependence of the adsorption process both on the functional groups on the hydroxyapatite and on the solution chemistry of the aqueous amino acids solutions. Copyright 2001 Academic Press.     

Radiochemical separation of99Mo from natural uranium irradiated with thermal neutrons

⁹⁹Mo was separated from uranium and insoluble fission product hydroxides. More than 98% of⁹⁹Mo radioactivity was extracted with bis (2-ethylhexyl)phosphoric acid. The organic phase was washed and⁹⁹Mo was back-extracted from the organic phase with NH₄OH solution. The percent recovery from the organic phase was 91% and the purity of⁹⁹Mo was more than 99%. Pure^99mTc was also extracted from the organic phase with a saline solution. Reversed-phase partition chromatography was used for the purification of⁹⁹Mo from¹³¹I and other fission products (10% HDEHP on kieselguhr bed).¹³¹I and other isotopes were quantitatively eluted with 0.1M H₂SO₄,⁹⁹Mo was eluted using a mixture of 0.5 M HCl and 30% H₂O₂.     

A Systematic Study of ZnO/CuO Core/Shell Nanostructures Pegylated by Microwave Assistant Reverse Micelles (RM) Method

In this work we synthesized ZnO/CuO nanostructures pegylated by simple and fast microwave method assistant reverse micelles, Reverse micelles protocol creates many advantages in stability, particle size control, morphology, density, loading level, distribution, uniformity, charge and purification. Based on the statistical results ZnO/CuO nanostructures placed in the hydrophilic substrate. The effect of microwave and concentration of surfactant on the surface area, pore diameter and pore volume of the final product was systematically studied using Taguchi technique. ZnO/CuO core/shell pegylated nanostructures, indicating a ZnO as core and CuO as shell and continuous micelles chains around this structures. Products were characterized by UV–Vis spectra, X-ray diffraction, scanning electron microscopy, Dynamic light scattering, Energy-dispersive X-ray spectroscopy, transmission electron microscopy and nitrogen adsorption (i.e. Brunauer–Emmett–Teller surface area analysis).     

Synthesis and antimicrobial evaluation of novel 1,3-thiazoles and unsymmetrical azines

Research on Chemical Intermediates - 1,3-Thiazol derivatives have been synthesized via reaction of 1-(1-(5,6-dimethoxy-2-oxobenzo[d]thiazol-3(2H)-yl)propan-2-ylidene)-4-substituted...     

Spectroelectrochemical and electrochromic behavior of poly(methylene blue) and poly(thionine)-modified multi-walled carbon nanotubes

Journal of Solid State Electrochemistry - The increasing efforts devoted to fabricating electrochromic (EC) devices have motivated a lot of studies to develop new EC materials. Herein, we introduce...     

Computational study on the effects of variable viscosity of micropolar liquids on heat transfer in a channel

Journal of Thermal Analysis and Calorimetry - A numerical model is developed to study the effects of temperature-dependent viscosity on heat transfer in magnetohydrodynamic flow of micropolar fluid...     

A mild and green chemistry approach for the synthesis of symmetrical spirooxindole derivatives

A simple and eco-friendly synthesis of the biologically important spirooxindole scaffold was done by the reaction of isatin with activated pyrazolones in the presence of a catalytic amount of p-toluenesulfonic acid in water at room temperature. A variety of symmetrical spirooxindole derivatives were obtained with excellent yields within short reaction time. This method is of great value because of its environmentally benign character, high yield, and easy handling.     

Thermoanalytical study of linkage isomerism in coordination compounds

The non-isothermal differential scanning calorimetry (DSC) experiments revealed that linkage isomerization of both pure trans-[Co(en)₂(ONO)₂]PF₆ (dinitrito isomer) and trans-[Co(en)₂(NO₂)₂]PF₆ (dinitro isomer) occurs in the solid state at elevated temperatures. The process was found to be exothermic for the dinitrito isomer and endothermic for dinitro isomer. The pure isomers could be considered to be in metastable states at ambient temperatures which would be converted to an equilibrium mixture of both isomers (stable state) upon heating. Since the isomerization of both isomers may be described as a two stages process, the corresponding DSC peaks have been resolved into two peaks by means of nonlinear curve fitting tools of PeakFit^® software. The resolution of the peaks helped us to determine enthalpy changes of stepwise isomerization of both isomers. A first-order initial rate and Kissinger methods have been employed to estimate kinetic parameters of the stepwise isomerization reactions. The Kissinger method provided more reliable kinetic results. The high activation energy and positive entropy changes of isomerization of both isomers are considered as indication of a dissociative mechanism in solid state.     

Fabrication and application of a new modified electrochemical sensor using nano-silica and a newly synthesized Schiff base for simultaneous determination of Cd,Cu and Hg ions in water and some foodstuff samples

A new chemically modified carbon paste electrode was constructed and used for rapid, simple, accurate, selective and highly sensitive simultaneous determination of cadmium, copper and mercury using square wave anodic stripping voltammetry (SWASV). The carbon paste electrode was modified by N,N′-bis(3-(2-thenylidenimino)propyl)piperazine coated silica nanoparticles. Compared with carbon paste electrode, the stripping peak currents had a significant increase at the modified electrode. Under the optimized conditions (deposition potential, −1.100 V vs. Ag/AgCl; deposition time, 60 s; resting time, 10 s; SW frequency, 25 Hz; pulse amplitude, 0.15 V; dc voltage step height, 4.4 mV), the detection limit was 0.3, 0.1 and 0.05 ng mL⁻¹ for the determination of Cd²⁺, Cu²⁺ and Hg²⁺, respectively. The complexation reaction of the ligand with several metal cations in methanol was studied and the stability constants of the complexes were obtained. The effects of different cations and anions on the simultaneous determination of metal ions were studied and it was found that the electrode is highly selective for the simultaneous determination of Cd²⁺, Cu²⁺ and Hg²⁺. Furthermore, the present method was applied to the determination of Cd²⁺, Cu²⁺ and Hg²⁺ in water and some foodstuff samples.