Nuclear Overhauser Effect Spectroscopy (NOESY) and 3JHH Coupling Measurements in the Determination of the Conformation of the Sesquiterpene Antimalarial Arteether in Solution

The twisting of the A-, B-, and D- rings of β-arteether were determined from dihedral angles derived from ³J_HH coupling constants and a Karplus-type equation that takes into account heteroatom substitution. The angles obtained by NMR were also compared to the angles obtained by molecular modeling and to those obtained from the methyoxyl analog (artemether) using x-ray crystallography. The NMR results showed that the A-ring was a relatively undistorted chair conformation with the 14-methyl group in an equatorial position. The NMR data indicated that the B-ring was very distorted and the D-ring was twisted outward because of the steric interactions with the ethoxy group. Two-dimensional NOESY data was used to measure selected proton-proton distances for arteether in solution and these distances were also compared to those obtained by molecular modeling and from the x-ray data for artemether. The NOESY data also indicated that the conformation of the A-ring was fairly normal, the B-ring was twisted, and the ethoxy group was in an extended conformation (C₁₁-C₁₂-O-C₁₆=+170°, and C₁₂-O-C₁₆-C₁₇=+169°)     

Effect of Ag-doping of nanosized FeMgO system on its structural, surface, spectral, and catalytic properties

The effects of Ag-doping on the physico-chemical, spectral, surface, and catalytic properties of the FeMgO system with various Fe₂O₃ loadings were investigated. The dopant (Ag) molar ratio varied between 0.01 % and 0.05 %. The techniques employed for characterisation of catalysts were TG/DTG, XRD, ESR, N₂ adsorption at ?196°C, and catalytic decomposition of H₂O₂ at 25?C35°C. The results obtained revealed that the investigated catalysts consisted of nanosized MgO as the major phase, apart from the MgFe₂O₄ and/or Fe₃O₄ phases. ESR result of the FeMgO system revealed the presence of paramagnetic species as a result of Ag-doping. The textural properties including SBET, porosity and St were modified by Ag-doping. The doping process with Ag-species improved the catalytic activity of the FeMgO system. Increasing the calcination temperature from 400°C to 800°C increased the catalytic activity (k*_{30 °C}) of 0.05 AgFeMgO in H₂O₂ decomposition by 21.2 times.     

Fabrication and electrical characterization of transparent NiO/ZnO p–n junction by the sol–gel spin coating method

Sol–gel spin technique was used to fabricate transparent p–n junction between NiO and ZnO semiconductors. Atomic force microscopy studies indicated that ZnO film had a fibrous structure, while NiO film showed very smooth surface morphology. The optical transmittance of these films was about 75 %. The optical band gaps of ZnO and NiO films were obtained to be 3.25 and 3.89 eV, respectively. The current–voltage characteristics of NiO/ZnO junction showed a good rectifying behavior. The junction parameters such as ideality factor and barrier height were calculated using thermionic emission model. The barrier height and ideality factor values of the diode were obtained to be 0.48 and 2.91 eV, respectively. The variation of photocurrent with wavelength indicates that this device had high efficiency in wavelength range of 450–475 nm.     

Many-valued quantum algebras

We deal with algebras of the same signature as MV-algebras which are a common extension of MV-algebras and orthomodular lattices, in the sense that (i) A bears a natural lattice structure, (ii) the elements a for which is a complement in the lattice form an orthomodular sublattice, and (iii) subalgebras whose elements commute are MV-algebras. We also discuss the connections with lattice-ordered effect algebras and prove that they form a variety. Supported by the Research and Development Council of the Czech Government via the project MSM6198959214.     

Solvent extraction of some nitroaromatic acids and their metal complexes from sulphuric acid by TBP and topo

Solvent extraction of 3,5-dinitrosalicylic (3,5-DNS) and 2-oxy-5-nitropyridinic (2-O-5-N-Py) acids and their Ni(II), Co(II) and Cu(II) complexes from sulphuric acid medium with TBP and TOPO in n-hexane was investigated. The compositions of the extractable species were determined by slope analysis. Possible utilization in separation processes is discussed in general.     

Propagation of surface waves at the interface between nonlinear MTMs and anisotropic materials

Metamaterials (MTMs), which have both negative permeability and negative permittivity, have potential applications in optoelectronics and communications. These materials are fabricated in laboratories which is an added advantage. The focus of this work is on the propagation of surface waves at the interface between nonlinear MTMs and anisotropic materials in the optical range. The dispersion equation is derived from Maxwell’s equations. The dispersion equation is solved numerically to study the characteristics of the propagated wave. Only TE modes are considered. The results display the dependence of the propagating waves on the characteristics of the structure composite materials.     

Protein Separation and Enzyme Purification by Preparative Capillary Isotachophoresis

The use of preparative capillary isotachophoresis (CITP), operating in a discontinuous fractionation mode, for separation and fast purification of the enzyme uridine diphosphate galactopyranose mutase (UGM) from the cell extract of Escherichia coli overproducing the recombinant enzyme is presented in this feasibility study. UGM is required to produce galactofuranose for the cell wall biosynthesis of many pathogenic microorganisms and represents a very attractive candidate for the development of new antimicrobial drugs. CITP separations were carried out under slightly alkaline pH conditions (8.7), in which UGM enzyme is negatively charged. Significantly simplified proteinous matrix isolated in several fractions by employed preparative CITP procedure with the aid of properly selected discrete spacers was subsequently confirmed by SDS PAGE with Coomassie staining. It was shown that preparative CITP is very effective tool for fast purification of the target enzyme from other proteinous matrix constituents when purification and isolation step lasted 20 min. The enzymatic activity of UGM was confirmed in the sample after the preparative CITP purification step, which is a crucial requirement for further biochemical applications.     

Impurity-profiling UPLC methods for quantitative analysis of some antiemetics formulated with pyridoxine

Cyclizine hydrochloride (CYC) and meclozine hydrochloride (MEC) are antihistaminic drugs generally co-formulated with pyridoxine hydrochloride (PYR) to treat nausea and vomiting in pregnancy. Several analytical techniques have been applied for the determination of CYC or MEC with PYR, but determination of CYC impurity; benzhydrol (BEH) or MEC impurity; or 4-chlorobenzophenone (BEP) has not been paid attention to. Therefore, micellar UPLC method is introduced for analysis of ternary mixtures containing PYR together with both CYC and BEH (mixture I) or MEC and BEP (mixture II). Chromatographic separation was achieved using a Hypersil gold C₈ column (50 × 2.1 mm, 1.9 μm) using 0.01 M sodium dodecyl sulfate modified to pH 3.5 using phosphoric acid:acetonitrile (45:55 by volume) for mixture I and 0.1% sodium dodecyl sulfate, 0.1% sodium bicarbonate adjusted to pH 2.6 by phosphoric acid:acetonitrile (47:53 by volume) for mixture II as mobile phases. The separated peaks were detected at 230 and 245 nm for mixtures I and II, respectively. The adopted methods were validated in conformance with the International Conference on Harmonization (ICH) recommendations and were properly applied in commercial pharmaceutical formulation analysis. Comprehensive ecological comparison was achieved, confirming a higher ecological value of the presented methods compared to the earlier reported methods.     

Contactless conductivity detection for screening myrosinase substrates by capillary electrophoresis

Myrosinase is a unique enzyme that catalyzes the hydrolysis of glucosinolates (GLS) to isothiocyanate (ITC), glucose and sulfate. Isothiocyanates display a diversified very interesting biological activity. In this study, capillary electrophoresis (CE) was used for the first time for evaluating myrosinase kinetics (maximum velocity V_max and Michaelis–Menten constant K_m) and to assess the affinity of a variety of substrates toward this enzyme.     

Simultaneous HPTLC and RP-HPLC methods for determination of bumadizone in the presence of its alkaline-induced degradation product

Accurate, selective, sensitive and precise HPTLC‐densitometric and RP‐HPLC methods were developed and validated for determination of bumadizone calcium semi‐hydrate in the presence of its alkaline‐induced degradation product and in pharmaceutical formulation. Method A uses HPTLC‐densitometry, depending on separation and quantitation of bumadizone and its alkaline‐induced degradation product on TLC silica gel 60 F₂₅₄ plates, using hexane–ethyl acetate–glacial acetic acid (8:2:0.2, v/v/v) as a mobile phase followed by densitometric measurement of the bands at 240 nm. Method B comprises RP‐HPLC separation of bumadizone and its alkaline‐induced degradation product using a mobile phase consisting of methanol–water–acetonitrile (20:30:50, v/v/v) on a Phenomenex C₁₈ column at a flow‐rate of 2 mL/min and UV detection at 235 nm. The proposed methods were successfully applied to the analysis of bumadizone either in bulk powder or in pharmaceutical formulation without interference from other dosage form additives, and the results were statistically compared with the established method. Copyright © 2011 John Wiley & Sons, Ltd.