Enantioseparation of novel psychoactive chiral amines and their mixture by capillary electrophoresis using cyclodextrins as chiral selectors

The prevalence of new psychoactive substances (NPS) has been increasing during the last decade as well as their constant growth of availability across the whole world. Regardless of the potential health hazard, NPS (often racemic compounds) are frequently sought after and abused for their psychoactive effects that may differ for individual enantiomers. In this work, capillary electrophoresis was used for the chiral separation of a mixture of eleven psychoactive chiral amines using β-cyclodextrin and carboxymethyl-β-cyclodextrin as chiral selectors at various concentrations. Chiral separation was successful for all the analytes studied. A mixture of these analytes was subsequently analyzed under optimal conditions, i.e., when using 20 mmol/L carboxymethyl-β-cyclodextrin in 50 mmol/L sodium phosphate buffer, pH 2.5. In this case, chiral separation occurred in nine out of eleven analytes. To our best knowledge, we achieved enantioseparations of seven analyzed compounds by CE for the first time.     

Enzyme action of the laccase-mediator system in the pulp delignification process

The present work aims a systematic kinetic investigation of the delignification action of the laccase-mediator system in the presence of oxygen. A dimensionless quantity a representing the degree of delignification was used as a criterion for the enzyme efficiency. It was found that the exponential equation which describes the kinetics of processes taking place on a uniformly inhomogeneous surface, fits the experimental results with the highest degree of statistical confidence. The activation energy Eobtained is independent of the delignification degree a, while the pre-exponential factor A decreases in the course of the process. It is mostly connected to the spatial limitations, the exhaustion of phenolic subunits available as well as to the decrease of the indirect activity of the non-phenolic structure in the lignin. This revised version was published online in June 2006 with corrections to the Cover Date.     

Production of Enantiopure Chiral Epoxides with E. coli Expressing Styrene Monooxygenase

Styrene monooxygenases are a group of highly selective enzymes able to catalyse the epoxidation of alkenes to corresponding chiral epoxides in excellent enantiopurity. Chiral compounds containing oxirane ring or products of their hydrolysis represent key building blocks and precursors in organic synthesis in the pharmaceutical industry, and many of them are produced on an industrial scale. Two-component recombinant styrene monooxygenase (SMO) from Marinobacterium litorale was expressed as a fused protein (StyAL2StyB) in Escherichia coli BL21(DE3). By high cell density fermentation, 35 g_DCW/L of biomass with overexpressed SMO was produced. SMO exhibited excellent stability, broad substrate specificity, and enantioselectivity, as it remained active for months and converted a group of alkenes to corresponding chiral epoxides in high enantiomeric excess (˃95–99% ee). Optically pure (S)-4-chlorostyrene oxide, (S)-allylbenzene oxide, (2R,5R)-1,2:5,6-diepoxyhexane, 2-(3-bromopropyl)oxirane, and (S)-4-(oxiran-2-yl)butan-1-ol were prepared by whole-cell SMO.     

电场或电磁场和光动力的协同效应对癌细胞失活和坏死的作用(英文)

应用弱正弦波电磁场改变细胞膜的穿透性并引起其失活和坏死.研究中,将人类癌细胞U 937和K 562放置于强度为10mT和39mT(50Hz)的正弦波电磁场内,并依次结合细胞毒素放线菌素 C以及其独特的光动力活性分别进行试验.     

Application of an Exponential Kinetic Equation to the Interaction of Optical Brighteners with Pulp

A bleached softwood kraft pulp was treated with fluorescent whitening agentsTinopal UP and Leucophor AP under different conditions. The kinetics ofadsorption-chemical interaction between optical brighteners and pulp wasdescribed by an exponential kinetic equation. An entropy heterogeneity of thepulp surface related to the active sorption centers, their accessibility and theirspatial orientation was confirmed. The activation energy values obtained werefound independent of the brightener concentration and on the increase of pulpwhiteness. A decisive role of the entropy factors was ascertained.     

Study of enzymatic reaction by electrophoretically mediated microanalysis in a partially filled capillary with indirect or direct detection

Electrophoretically mediated microanalysis (EMMA), in combination with a partial filling technique and indirect or direct detection, is described for the study of enzymes reacting with the high mobility inorganic or organic anions as substrates or products. Part of the capillary is filled with a buffer optimized for the enzymatic reaction, the rest of the capillary with the background electrolyte being optimal for the separation of substrates and products. With haloalkane dehalogenase, chosen as a model enzyme, the enzymatic reaction was performed in a 20 mM glycine buffer (pH 8.6). Because of the wide substrate specificity of this enzyme, utilizing chlorinated as well as brominated substrates and producing either nonabsorbing chloride or absorbing bromide ions, two different background electrolytes and detection approaches were adopted. A 10 mM chromate-0.1 mM cetyltrimethylammonium bromide background electrolyte (pH 9.2) was used in combination with indirect detection and 20 mM beta-alanine-hydrochloric acid (pH 3.5) in combination with direct detection. The Michaelis constant (K(m)) of haloalkane dehalogenase for 1-bromobutane was determined. The K(m) values 0.59 mM estimated by means of indirect detection method and 0.17 mM by means of direct detection method were comparable with the value 0.13 mM estimated previously by gas chromatography.     

Dynamics of counterions in polyelectrolyte multilayers studied by electro-optics

The electro-optical behavior of a multilayer constructed via layer-by-layer deposition of poly(sodium 4-styrenesulfonate) (PSS) and poly(allylamine hydrochloride) (PAH) onto ellipsoidal β-FeOOH particles is examined using electric light scattering method. For fully charged polymers (at pH 4.5), the electro-optical effect is found to increase with polyelectrolyte layer number, showing a tendency to saturation in the linear growth regime. The effect is greater and of lower frequency of relaxation for the films ending with PAH in comparison to those with top PSS layer. Evidence is given that polarization of “condensed” counterions along the chains of the last-adsorbed polymer is mainly responsible for the observed electro-optical behavior of the polyelectrolyte multilayer. Although incorporation of “condensed” small ions into the film bulk seems probable for the PSS/PAH multilayer, their participation in the electro-optical effect is found negligible. The structural changes in the PSS/PAH multilayer due to the PAH deprotonation at pH 7.5 and the corresponding changes in the electro-optical effect confirm the key role of the last-adsorbed polymer for the behavior of the entire PSS/PAH film.     

Unusual dispersion of the electro-optically determined electric polarizability of bentonite dispersed particles in the range 10 kHz — 1 MHz

An unusual dispersion of the electric light scattering by aqueous calcium bentonite is observed. The electro-optic effect rises with the increase of the frequency in the range 10 kHz — 1 MHz. Parallel measurements are made on suspensions of sodium bentonite and zetlizer kaolinite at different ionic strengths and particle dimensions. It is shown that the dispersion for calcium bentonite does not greatly depend on the concentration of the indifferent electrolyte (sodium chloride with concentrations 10^–4 and 5.10^–4 M/l) or on the suspension concentration. Several possibilities for explaning this unusual dispersion are considered.     

Thermodynamic aspects of the adsorption of an optical brightener on pulp

Optical brighteners Tinopal UP and Leucophor AP are used in additional treatment of bleached softwood kraft pulp under different conditions. The present paper describes the applicability of Temkin adsorption isotherm to characterize the thermodynamic equilibrium reached in chemisorption of an optical brightener on pulp’s uniformly non-homogeneous surface. It is found that this is an endothermic process. The entropy factors dominate the developing non-homogeneity and hence the variation of the Gibbs’s free energy as well.     

Numerical Modelling of Newtonian and Non-Newtonian Fluids Flow

The work deals with numerical modelling of 2D/3D laminar incompressible viscous flows for Newtonian and non–Newtonian fluids. The unsteady system of Navier–Stokes equations with steady boundary conditions in the form of an artificial compressibility method is solved by multistage Runge–Kutta finite volume method. Steady state solution is achieved for t→∞. Convergence is followed by steady residual behaviour. For unsteady solution high compressibility coefficient β² is considered. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)