Journal of the Iranian Chemical Society
Volume:4 Issue: 3, Sept 2007

The enzyme Na+, K+-ATPase is an integral membrane protein which transports sodium and potassium cations against an electrochemical gradient. The transport of Na+ and K+ ions is connected to an oscillation of the enzyme between the two conformational states, the E1 (Na+) and the E2 (K+) conformations. The enzymatic activity of ATPase is largley affected by different ligands complexation. This review reports the effects of several drugs such as AZT (anti-AIDS), cis-Pt (antitumor), aspirin (anti-inflammatory) and vitamin C (antioxidant) on the stability and secondary structure of Na,K-ATPase in vitro. Drug-enzyme binding is mainly through H-bonding to the polypeptide C=O and C-N groups with two binding constants K1(AZT) = 5.30 × 105 M-1 and K2(AZT) = 9.80 × 103 M-1 for AZT and one binding constant for Kcis-Pt = 1.93 × 104 M-1, Kaspirin = 6.45 × 103 M-1 and Kascorbate = 1.04 × 104 M-1 for cis-Pt, aspirin and ascorbic acid. The enzyme secondary structure was altered from that of α-helix 19.8% (free protein) to almost 22-26% and the b-sheet from 25.6% to 18-22%, upon drug complexation with the order of induced stability AZT > cis-Pt > ascorbate > aspirin.

The single crystal X-ray data of a novel 3D coordination polymer of Mn(II) with 1,3-bis(4-pyridyl)propane (bpp) and anionic chloride ligands, [Mn(µ-bpp)2Cl2]n, show that the coordination environment around the Mn(II) is a distorted octahedral. The thermal stability of the compound was studied by thermal gravimetric and differential thermal analyses. The luminescent spectrum of the compound in solution indicates intense fluorescent emission at 368 nm.

An efficient, simple and solvent-free method for highly regioselective N-alkylation of benzotriazole in the presence of SiO2, K2CO3 and tetrabutylammonium bromide (TBAB) under thermal and microwave conditions has been described. In this method, 1-alkyl benzotriazoles were obtained regioselectively in moderate to high yields and short reaction times.

The kinetics and mechanism for the thermal decomposition of 1,2-dichloroethane (EDC) was studied in a flow system over the temperature range of 849-1064 K and pressure range of 10-300 Torr under homogeneous conditions in a tubular quartz reactor. Gas chromatography was used to measure the concentration of products. Four-center HCl elimination was found to be the most important channel in this system. Minor products such as methane, ethylene, acetylene, chloroethane, and chloroprene were identified. Ab initio calculations at the DFT, CASMP2, and QCISD(T) levels of theory were carried out to investigate the mechanism of this system and to calculate necessary parameters to compute the rate constants of different steps. Dependence of formation of vinyl chloride on the total pressure is measured, experimentally.

Copper(II) salts were combined with a tetrapyrazolyl ligand ({N,N,N’,N’-tetrakis-[(3,5-dimethylpyrazol-1-yl)methyl)-1,4-phenylenediamine}L1 or {N,N,N’,N’-tetrakis-[(1,5-dimethylpyrazol-3-yl)methyl)-1,4-phenylenediamine}L2) and assessed as oxidation catalysts. The corresponding dioxygen complexes were generated in situ by mixing the copper salt and the pyrazolyl donor ligand in air. The oxidation of 3,5-di-tert-butylcatechol (DTBC), which affords 3,5-di-tert-butylquinone (DTBQ), was studied. The reaction rate was found to depend essentially on the nature of the junction linking two pyrazolyl neighbours.

Electrocatalytic oxidation of methanol on a glassy carbon electrode coated with Ni(II)-(1,2-phenylendiamine)2 (GC/NiOPD), conditioned by the potential recycling in a potential range of 100-650 mV (vs. SCE) is studied by cyclic voltammetry in an alkaline medium (0.10 M NaOH). The results show that the NiOPD layer formed at the surface of the electrode behaves as an efficient electrocatalyst for the oxidation of methanol in the alkaline medium via the Ni(ІІІ) species with a cross exchange reaction occurring throughout the layer at a low concentration of methanol. The effects of various parameters such as potential scan rates, methanol concentration and NiOPD surface concentration on the electro-oxidation of methanol are also investigated.

We studied the means by which DNA-dendronized polymer nanoclusters and the nanoclusteration process are affected by structural properties of the nanocluster components, including the length of dendronized polymer, wrapping radius of DNA, and surface charge densities on the DNA and dendronized polymer, by calculating the total free energy of the system and free energy of the nanoclusteration process. The most thermodynamically stable nanocluster conformation was then predicted based on the values of the free energies. It was found that the nanoclusters with longer dendronized polymers, shorter DNA wrapping radius, and larger surface charge density on both the DNA and dendronized polymers are more stable.

In this work, we used a statistical associating fluid theory to analyze two important thermodynamic regularities for some associating fluids, including water, methanol and ethanol. The studied regularities included: (i) the common bulk modulus point on the isotherms of the reduced bulk modulus versus reduced density, (ii) near linearity of the reduced isothermal bulk modulus as a function of reduced pressure. In this work, we also reported the influence of the molecular size and interaction strength on the bulk modulus point.

In this study, the synthesis and characterization of some phosphoramides are reported. In addition, their insecticidal activity and probable toxicity were predicted using the PASS software. Partial multiple bond formation and charge distribution may be responsible for the anti-AChE activity in phosphoramides.

Silica chloride as an efficient solid acid can serve as an eco-friendly and high-capacity reagent for the deprotection of trimethylsilyl ethers to their corresponding alcohols under mild and heterogeneous conditions. The yields are excellent and the procedure is simple and convenient, with the higher catalytic efficiency of a heterogeneous system.

The synthesis of p-nitrobenzoic acid and benzoic acids from benzyl and methyl ketones has been described using cerium(IV) ammonium nitrate in acetic acid. This simple method for the oxidation of benzylic ketones can be used as a practical method for the synthesis of 4-nitrobenzoic acid.

Zr(HSO4)4 as a solid acid was applied for the acetalization of carbonyl compounds, at room temperature, under solvent-free conditions with good to excellent yields. The low cost and availability of the reagents, versatile procedure and easy work-up make this method attractive for the organic synthesis of these compounds.

Cobalt cerium oxides, prepared using a co-precipitation procedure, were studied as catalysts for the conversion of synthesis gas to light olefins (C2-C4). Specifically, we studied the effect of a range of preparation variables, including the molar ratio of the [Co]/[Ce] of the precipitation solution, ageing time and calcination temperature. In addition, the effects of supports and promoters on the catalysts’ activity and selectivity and a range of reaction temperatures using synthesis gas with different H2/CO molar feed ratios were investigated. The catalyst containing a molar ratio of 80% Co and 20% Ce, aged for 2 h, supported with 15 wt% SiO2 without any promoter, at an operating temperature of 450 ºC and an H2/CO feed ratio of 2/1 (GHSV = 4500 h-1), performed optimally for the conversion of synthesis gas to light olefins. The characterization of both the precursors and the calcined catalysts by powder X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller specific surface area measurements and thermal analysis methods, including TGA and DSC, show that all the preparation variables influenced the catalyst precursor structure.

The synthesis of amides and phenylhydrazides from the reaction of corresponding carboxylic acids with primary aliphatic, aromatic amines or phenylhydrazine in the presence of triethylamine or diisopropylethyl amine as a base using 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU) proceeds smoothly under mild conditions to afford the corresponding amides or phenylhydrazides in good to high yields in ethyl acetate at room temperature.

An efficient and selective protection of various structurally and electronically divergent aryl and aliphatic amines with Cbz-Cl in the presence of a catalytic amount of molecular iodine (2 mol%) in methanol with high yields at ambient temperature is presented.