Enantiorecognition of profens by capillary electrophoresis using a novel chiral selector eremomycin

The evaluation of a macrocyclic glycopeptide antibiotic, eremomycin, as a chiral selector in capillary electrophoresis (CE) has been performed. The stability of eremomycin in solution and capillary electrolyte, as well as its optical and electrophoretic properties have been discussed. The effect of experimental parameters influencing the enantioseparation of several profens has been studied. Excellent enantioseparation of profens has been achieved and migration order has been validated. Comparison of enantioseparations of profens in CE by using eremomycin-mediated electrolytes and in HPLC with eremomycin immobilized on silica has revealed similar trends for both methods.     

Infra-red and electronic absorption spectra of 2-bromopyrimidine

The electronic absorption spectrum of 2-bromopyrimidine in the u.v. region has been recorded in vapour phase and in solution phase in different solvents. Only one system has been observed in vapour phase and it has been identified as π* ← n transition. In solution phase two systems have been identified. The system on the longer wavelength side has been identified as corresponding to the one observed in vapour phase while the other one has been assigned to a π* ← π transition. The infrared spectrum of this molecule has also been recorded and analysed. Help of these i.r. data has been taken to analyse the u.v. spectrum of 2-bromopyrimidine, considering the molecule as belonging to C_2υ point group.     

A taylor series model to evaluate the interelemental effects in X-ray fluorescence analysis, applied to the iron-zirconium-diluent system

A semi-empirical model has been developed to quantify the interelemental effects in X-ray fluorescence analysis. The measured X-ray fluorescence intensity has been expressed as a function of the different fluorescence elements composing the sample. this complex function has become an operative function via a Taylor series development. An explication has been given for the significance of the different terms of the series. These terms respond to mathematical functions known as characteristic functions for each chemical system. A parameter (B) has been defined which makes it possible to quantify the influence of the interelemental effect as a function of the analyte concentration (C) and that of the concomitant elements. The proposed model has been applied to the Fe-Zr-diluent chemical system. Simple relationships between B vs C have been obtained independently considering iron or zirconium as analyte.     

The field dependence of mobility in molecularly doped polymers under the conditions of nonequilibrium transport

A multiple-trapping model has been used to numerically analyze the effects of the nonequilibrium transport of holes on the field dependence of drift mobility as obtained in a time-of-flight experiment. The intrinsic field dependence has been assigned to the frequency factor in the form of the Poole-Frenkel law. Strongly dispersive transport, as well as a nonequilibrium-charge-transfer regime given by the Gaussian disorder model, has been considered. It has been established that the currently accepted approach to the analysis of the field dependence of mobility needs to be reexamined.     

Improvement of properties of silica‐filled styrene‐butadiene rubber composites through plasma surface modification of silica

The performance of plasma surface modified silica filler in styrene‐butadiene rubber (SBR) matrix has been analyzed. The conditions of plasma modification have been optimized by taking secant modulus as a standard parameter and the occurrence of the modification has been confirmed by surface area determination and Fourier transform infrared spectroscopy. The plasma‐modified surface of silica has been found to be composed of carbon–carbon double bonds and carbon–hydrogen bonds. Silane treatment also has been carried out on silica filler surface for a comparative assessment of its influence in the curing behavior and filler–rubber interaction. The cure reactions of all the rubber compounds have been found to be proceeded according to first‐order kinetics. A reduction in the cure reaction rate constant has been observed with the loading of unmodified and surface modified silica, emphasizing the cure deactivation of the matrix rubber by the silica filler. The filler dispersion, as revealed by scanning electron microscopy, has been found to be greatly improved by the plasma as well as silane treatment. The filler–rubber interaction has been found to be greatly improved by both surface treatments, but the best balance of mechanical properties has been observed with plasma surface modification only. Copyright © 2004 John Wiley & Sons, Ltd.     

Many-orbital cluster expansion for the exchange-repulsion nonadditivity in the interaction of rare gas atoms. The neon trimer

Nonadditivity of the exchange repulsion for three neon atoms in the equilateral triangle configuration has been calculated in the first-order of the symmetry adapted perturbation theory. The relative nonadditive contribution to the first-order interaction energy has been found to be about twice as small as in the helium trimer. The many-orbital cluster partition of the exchange nonadditivity has been derived. It has been found that in the region of the van der Waals minimum about 95% of the exchange nonadditivity originates from the interaction of the L-shell electrons only. The five-orbital terms as well as terms of an order-higher than S³ have been found to be negligible. Approximate formulae for evaluation of the exchange repulsion nonadditivity has been proposed and discussed.This work was partly supported by the Polish Academy of Sciences within the project MR.I.9.     

Synthesis of biocompatible hydrophobic silica-gelatin nano-hybrid by sol-gel process

Silica-biopolymer hybrid has been synthesised using colloidal silica as the precursor for silica and gelatin as the biopolymer counterpart. The surface modification of the hybrid material has been done with methyltrimethoxysilane leading to the formation of biocompatible hydrophobic silica-gelatin hybrid. Here we are reporting hydrophobic silica-gelatin hybrid and coating precursor for the first time. The hybrid gel has been evaluated for chemical modification, thermal degradation, hydrophobicity, particle size, transparency under the UV-visible region and morphology. FTIR spectroscopy has been used to verify the presence of CH(3) groups which introduce hydrophobicity to the SiO2-MTMS-gelatin hybrids. The hydrophobic property has also been tailored by varying the concentration of methyltrimethoxysilane. Contact angle by Wilhelmy plate method of transparent hydrophobic silica-gelatin coatings has been found to be as high as approximately 95 degrees . Oxidation of the organic group which induces the hydrophobic character occurs at 530 degrees C which indicates that the surface hydrophobicity is retained up to that temperature. Optical transmittance of SiO2-MTMS-gelatin hybrid coatings on glass substrates has been found to be close to 100% which will enable the hybrid for possible optical applications and also for preparation of transparent biocompatible hydrophobic coatings on biological substrates such as leather.     

Characteristic monomials with chirality fittingness for combinatorial enumeration of isomers with chiral and achiral ligands

A new method of combinatorial enumeration based on characteristic monomials with chirality fittingness (CM-CFs) has been proposed in order to enumerate isomers with chiral ligands as well as with achiral ones. The CM-CFs have been defined as monomials that consist of three kinds of dummy variables in light of the subduction of the Q-conjugacy representations for chiral and achiral cyclic groups. A procedure of calculating CM-CFs for cyclic groups and finite groups has been discribed so as to tabulate them as CM-CF tables. Then the CM-CF method has been applied to the enumeration of isomers with achiral ligands as well as chiral ones.     

Determination of lipase activity in porcine pancreas and clinical analysis of lipase in human serum with surface acoustic wave enzyme sensor system

A new kind of surface acoustic wave (SAW) enzyme sensor system has been applied to the assay of extracted lipase activity based on triacetin solution as substrate. A linear relationship between the frequency change and the enzyme activity up to 500 U/L has been obtained, and the detection limit has been evaluated to 0.3 U/L. Kinetic parameters of the extracted lipase as well as that of the standard enzyme have been estimated. The effects of temperature, pH value and surfactants have been investigated. A comparison between SAW sensor system and the conductometric method has been carried out. The technique has been applied to the determination of lipase activity in serum samples. Received: 17 January 1995 / Revised: 9 March 1995 / Accepted: 16 March 1995 Correspondence to: Shouzhuo Yao     

Electromembrane extraction from biological fluids

Electro-assisted extraction of ionic drugs from biological fluids through a supported liquid membrane (SLM) and into an aqueous acceptor solution was recently introduced as a new sample preparation technique termed electromembrane extraction (EME). The applied electrical potential across the SLM has typically been in the range of 1-300 V. Successful extractions have been demonstrated even with common batteries (9 V) instead of a power supply. The chemical composition of the SLM has been crucial for the selectivity and for the recoveries of the extraction. Compared to other liquid-phase microextraction techniques (LPME), extraction times have been reduced by a factor of 6-17, and successful extractions have been obtained at extraction times of 1-5 min, and even down to a few seconds with online microfluidic EME devices. The technique has provided very efficient sample clean-up and has been found well suited for the extraction of sample sizes in the low μL range. Extractions have been performed with both rod-shaped hydrophobic porous fibers and with flat hydrophobic porous sheets as SLM support. The technique has been successfully downscaled into the micro-chip format. The nature of the SLM has been tuned for extraction of drugs with different polarity allowing extractions to be tailored for specific applications depending on the analyte of interest. The technique has been found to be compatible with a wide range of biological fluids and extraction of drugs directly from untreated human plasma and whole blood has been demonstrated. EME selectively extracts the compounds from the complex biological sample matrix as well as allowing concentration of the drugs. With home-built equipment fully acceptable validation results have been obtained.     

Synthesis and absolute configuration of three natural ent-halimanolides with biological activity

The first three natural ent-halimanolides known until now have been synthesized from ent-halimic acid. Their structure have been confirmed as well as their absolute configurations established. Bestmann methodology has been used for the synthesis of butenolides and for the γ-hydroxybutenolides synthesis the Boukouvalas method has been employed. Biological testing has been carried out on these compounds.     

LiF-KF熔盐溶液局部结构的计算机模拟研究

本文用Monte Carlo法对同离子系LiF-KF熔盐溶液的局部结构进行了计算机模拟,介绍了计算方法和模型。计算了LiF, KF及Lif-KF混合前后正-正离子, 正-负离子, 负-负离子间位能变化, 各类离子的近邻离子排布规律, 以及各种形式离子团的组成比例。本文还讨论了在熔盐瞬时结构中存在的静电场的微区涨落。     

Characterization of 17α-hydroxysteroid dehydrogenase activity (17α-HSD) and its involvement in the biosynthesis of epitestosterone

Background  

Epi-testosterone (epiT) is the 17α-epimer of testosterone. It has been found at similar level as testosterone in human biological fluids. This steroid has thus been used as a natural internal standard for assessing testosterone abuse in sports. EpiT has been also shown to accumulate in mammary cyst fluid and in human prostate. It was found to possess antiandrogenic activity as well as neuroprotective effects. So far, the exact pathway leading to the formation of epiT has not been elucidated.     

Contactless Conductivity Detection in Capillary Electrophoresis: A Review

The popularity of contactless conductivity detection in capillary electrophoresis has been growing steadily over the last few years. Improvements have been made in the design of the detector in order to facilitate its handling, to allow easy incorporation into available instruments or to achieve higher sensitivity. The understanding of its fundamental working principles has been advanced and the detection approach has also been transferred to lab‐on‐chip devices. The range of applications has been extended greatly from the initial work on small inorganic ions to include organic species and biomolecules. Concurrent determination of cations and anions by dual injection from opposite ends has been demonstrated as well as sample introduction by using flow‐injection systems for easy automation of the process.     

On temperature- and space-dimension dependent matter agglomerations in a mature growing stage

Model matter agglomerations, with temperature as leading control parameter, have been considered, and some of their characteristics have been studied. The primary interest has been focused on the grain volume fluctuations, the magnitude of which readily differentiates between two commonly encountered types of matter agglomeration/aggregation processes, observed roughly for high- and low-density matter organizations. The two distinguished types of matter arrangements have been described through the (entropic) potential driving the system. The impact of the potential type on the character of matter agglomeration has been studied, preferentially for (low-density) matter aggregation for which a logarithmic measure of its speed has been proposed. A common matter diffusion as well as mechanical relaxation picture, emerging during the mature growing stage, has been drawn using a phenomenological line of argumentation. Applications, mostly towards obtaining soft agglomerates or so-called jammed materials, have been mentioned.     

THE HALOID DISPLACEMENT BY AMMONIA AND AMINES IN 2(3)-CHLORO-3(2)-ALKYLTHIO-2-METHYLPROPANOIC ACID DERIVATIVES

Abstract

The reaction of derivatives of 2(3)-chloro-3(2)-alkylthio-2-methylpropanoic acids with ammonia in nitromethane has been found to yield a mixture of 2-and 3-aminosubstituted compounds. With dimethylamine and diethylamine in nitromethane (sulfolane) a mixture of alkylamino-substituted products as well as HCl elimination products has been obtained. Pure diethylamine has been shown to form mainly the products of HCl elimination. A mechanism for the displacement and elimination reactions via formation of various episulphonium ions as intermediates has been suggested.     

Studies in chemical ionization mass spectrometry of some flavonoids

Formation of ions in chemical ionization mass spectrometry of flavonoid compounds has been studied. Production of adduct ions and fragment ions as a function of ring substituents and of reagent gas has been observed. Pressure and repeller field dependence of ions has been found as a function of ring substituents.     

C-H Group as proton donor by formation of a weak hydrogen bond

A systematic CNDO/2 study has been carried out on the weak C-H...F, C-H...O, and C-H...N hydrogen bonds. An H-bond formation has been revealed for proton donors with negative excess charge on the hydrogen. The concept of the positive character of the hydrogen as well as some essential features of the hydrogen bond have been discussed. Some useful correlations have been found and the importance of the charge shifts has been emphasized.     

On the solution of one classical problem in vibrational spectroscopy

The identification of the structure of molecules from their vibrational spectra has been considered as an inverse spectral problem. A statement of the problem has been formulated and an algorithm has been treated for its solution. Conditions for obtaining a unique solution have been analyzed. An attempt has been made to evaluate the possibility of distinguishing isomers by calculating their vibrational spectra.