The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
Jingwu Kang - One of the best experts on this subject based on the ideXlab platform.
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Enzyme inhibitor screening by CE with an on-column immobilized enzyme microreactor created by an ionic binding technique.
Methods in molecular biology (Clifton N.J.), 2013Co-Authors: Chao Liu, Qianqian Zhang, Jingwu KangAbstract:Enzymes are an important class of drug targets. In the early stage of the drug discovery, the major task is to find out the inhibitors of a given enzyme target in a compound library. Herein we describe a method for screening the enzyme inhibitors in the complex mixtures (such as the natural extracts) by capillary electrophoresis with an on-column immobilized enzyme microreactor. The enzyme molecules are immobilized on the capillary wall via ionic binding with the positively charged coating, which was created by simply flushing the column with a solution of polyelectrolyte Hexadimethrine Bromide. The activities of the immobilized enzymes are assayed by performing the electrophoretic separation and thereafter determining the product of the enzyme-mediated reaction. Enzyme inhibition can be read out directly from the reduced peak area of product in comparison with that in the reference electropherogram obtained in the absence of any inhibitor.
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Use of macrocyclic antibiotics as the chiral selectors in capillary electrophoresis.
Methods in molecular biology (Clifton N.J.), 2012Co-Authors: Jingwu KangAbstract:Macrocyclic antibiotics, especially vancomycin, represent a class of versatile chiral selectors for enantioseparations by capillary electrophoresis (CE). In this chapter, we describe the protocol for performing CE enantioseparations with vancomycin as the chiral selector. Dynamic coating of the capillary with polymers including the positively charged polyelectrolyte Hexadimethrine Bromide or electro-neutral poly(dimethylacrylamide) proved to be very useful in order to reduce the adsorption of vancomycin onto the capillary wall resulting in an improved separation efficiency. The partial filling technique is employed for improvement of the detection sensitivity. Utilization of these techniques makes the CE enantioseparation with vancomycin more practical and robust.
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Enantioseparation by CE with vancomycin as chiral selector: Improving the separation performance by dynamic coating of the capillary with poly(dimethylacrylamide).
Electrophoresis, 2007Co-Authors: Zhaoyan Wang, Junfeng Wang, Jingwu KangAbstract:An approach for improving the separation performance of the enantioseparation by CE with vancomycin as chiral selector is described. In the present method, a solution of poly(dimethylacrylamide) (PDMA) was used for dynamic coating of the capillary wall to minimize the adsorption of vancomycin onto the capillary wall, and to depress the EOF. Compared with the bare fused-silica capillaries and the capillaries coated with the polycationic polymer Hexadimethrine Bromide (HDB), the PDMA-coated capillary displayed the best separation performance. The resulting coating could withstand hundreds of runs without losing its function. Moreover, a partial filling technique was applied to avoid interference in detection caused by the presence of vancomycin in the buffer. The separation time was shortened when a short-end-injection technique was applied. Several parameters such as buffer pH, vancomycin concentration and plug length of the vancomycin solution for the separation were optimized. Under the optimal conditions, all tested enantiomers, including FMOC amino acids derivatives, ketoprofen and fenoprofen, were baseline-separated in less than 4.2 min.
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enzyme inhibitor screening by capillary electrophoresis with an on column immobilized enzyme microreactor created by an ionic binding technique
Analytical Chemistry, 2006Co-Authors: Zhongmei Tang, Jingwu KangAbstract:A novel strategy for screening the enzyme inhibitors from the complex mixtures by capillary electrophoresis with an on-column immobilized enzyme microreactor created by an ionic binding technique is reported. The enzyme microreactor was prepared in two steps: First, the capillary wall was dynamically coated with a polycationic electrolyte Hexadimethrine Bromide (HDB) by simply flushing the column using the HDB solution. Subsequently, a plug of the enzyme solution was injected and incubated for 5 min to permit the enzyme molecules to immobilize on the positively charged coating via ionic binding. To demonstrate this strategy, angiotensin-converting enzyme (ACE) was employed as a model for the enzyme immobilization, inhibition study, and inhibitor screening. It has been proved that such a prepared immobilized ACE microreactor displays a high enough activity and stability. Furthermore, the immobilized enzyme microreactor could be easily renewed. The inhibition study or inhibitor screening was accomplished t...
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Separation of atropisomers of anti-hepatitis drug dimethyl diphenyl bicarboxylate analogues by capillary electrophoresis with vancomycin as the chiral selector.
Journal of chromatography. A, 2006Co-Authors: Wenhua Gao, Jingwu KangAbstract:Separation of atropisomers of analogues of the anti-hepatitis drug dimethyl diphenyl bicarboxylate (DDB) by capillary electrophoresis with vancomycin as the chiral selector is described. Among several tested chiral selectors, including various cyclodextrin derivatives as well as vancomycin, only the latter displayed the enantioselectivity to the studied atropisomers. However, relatively poor separation efficiency was obtained due to the adsorption of vancomycin on the capillary wall. This problem was overcome by modifying the capillary wall with a polycationic electrolyte named Hexadimethrine Bromide (HDB) to produce a positively charged coating, which minimized the adsorption of vancomycin on the capillary wall by electrostatic repulsion. Moreover, the positively charged coating could shorten the separation time by reversing the EOF because the reversed EOF migrated to the same direction as the negatively charged analyte. Effects of buffer pH, vancomycin and buffer concentrations and applied voltage on the separation were investigated and the optimal conditions were established as follows: 40 mM Tris-phosphate buffer (pH 6.0) containing 6.0 mM vancomycin and 0.001% HDB. Baseline separation of three racemic DDB analogues was obtained within 12 min under the optimal conditions.
Akira Matsuoka - One of the best experts on this subject based on the ideXlab platform.
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Improved method for measuring tartrate-resistant acid phosphatase activity in serum
2015Co-Authors: Akira MatsuokaAbstract:We describe an improved method for the kinetic mea-surement of tartrate-resistant acid phosphatase (TrACP; EC 3.1.3.2) activity in serum. Of the TrACP derived from erythrocytes, platelets, and macrophages (osteoclasts and others), that from the first two sources is also resistant to fluoride, whereas skeletal TrACP is sensi-tive to fluoride. Thus, osteoclast-derived TrACP can be measured specifically by exploiting its sensitivity to fluoride. We measured the activity of tartrate-resistant and fluoride-sensitive acid phosphatase (TrFsACP) by using 2,6-dichloro-4-acetylphenyl phosphate as sub-strate at pH 6.2. The activity of TrFsACP in serum was increased by adding Hexadimethrine Bromide (Poly-brene) to the reaction mixture. This method was not influenced by hemolysis with hemoglobin concentra
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Improved method for measuring tartrate-resistant acid phosphatase activity in serum
Clinical chemistry, 1998Co-Authors: Mamoru Nakanishi, Kousei Yoh, Kagehiro Uchida, Souji Maruo, Akira MatsuokaAbstract:We describe an improved method for the kinetic measurement of tartrate-resistant acid phosphatase (TrACP; EC [3.1.3.2][1]) activity in serum. Of the TrACP derived from erythrocytes, platelets, and macrophages (osteoclasts and others), that from the first two sources is also resistant to fluoride, whereas skeletal TrACP is sensitive to fluoride. Thus, osteoclast-derived TrACP can be measured specifically by exploiting its sensitivity to fluoride. We measured the activity of tartrate-resistant and fluoride-sensitive acid phosphatase (TrFsACP) by using 2,6-dichloro-4-acetylphenyl phosphate as substrate at pH 6.2. The activity of TrFsACP in serum was increased by adding Hexadimethrine Bromide (Polybrene) to the reaction mixture. This method was not influenced by hemolysis with hemoglobin concentrations as great as 0.9 g/L. The mean ± SD values of TrFsACP activity by this method were 20.4 ± 2.8 and 16.4 ± 2.3 U/L for young (ages 20–29 years) men (n = 34) and women (n = 50), respectively. The highest mean TrFsACP activity was found among children younger than 15 years, followed by that in elderly subjects (older than 60). [1]: pending:yes
Andreas Zemann - One of the best experts on this subject based on the ideXlab platform.
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High-speed separation of carboxylic acids by co-electroosmotic capillary electrophoresis with direct and indirect UV detection
Journal of Chromatography A, 1997Co-Authors: Dietmar Volgger, Andreas Zemann, Günther K. Bonn, Michael Jerry AntalAbstract:The separation of saturated and unsaturated mono- and dicarboxylic acids which are intermediates and reaction products in the conversion pathway of citric acid and itaconic acid in hot, compressed liquid water and supercritical water is performed with co-electroosmotic high-performance capillary electrophoresis. Both direct as well as indirect photometric detection can be carried out at a wavelength of 185 nm. Co-electroosmotic separation conditions are set up by adding 1,5-dimethyl-1,5-diazaundecamethylene polymethoBromide (Hexadimethrine Bromide; HDB; polybrene) as an electroosmotic flow modifier to achieve fast separations in the range of minutes and below. The quantitative results achieved with direct and indirect UV detection are in good comparison with the values of published HPLC data. Using this method, process control is possible by fast component monitoring of the reaction solutions.
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Sub-minute separations of organic and inorganic anions with co-electroosmotic capillary electrophoresis
Journal of Chromatography A, 1997Co-Authors: Andreas ZemannAbstract:Abstract Fast capillary electrophoretic separations of various classes of anionic compounds are performed by using very short effective separation lengths in addition to a similarly directed movement of the electroosmotic flow and the inherent electrophoretic mobilities of the analytes. A polycationic surfactant (Hexadimethrine Bromide) is added to the electrolyte, which dynamically coats the inner surface of the capillary and causes a fast anodic electroosmotic flow. Selective separations in the sub-minute range combined with high separation efficiencies of several hundred thousands theoretical plates per meter effective separation length can be achieved if organic solvents or mixtures thereof are added to the electrolytes. The methods are used for the high-speed separation of various anionic analytes, such as carbohydrates, carboxylic acids, phenolic compounds and inorganic anions.
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Fast separation of underivatized carbohydrates by coelectroosmotic capillary electrophoresis
Electrophoresis, 1997Co-Authors: Andreas Zemann, D. T. Nguyen, Günther K. BonnAbstract:A method for the rapid quantitative analysis of underivatized acidic sugars, monosaccharides and disaccharides using coelectroosmotic capillary electrophoresis was developed. Indirect UV detection at 254 nm using sorbate as background electrolyte was employed for monitoring the analytes. A highly alkaline pH value of the electrolyte system was chosen in order to achieve an electrophoretic mobility of the saccharides towards the anode. A dynamic reversal of the electroosmotic flow and, by this means, a codirectional movement of the negatively charged analytes and the electroosmotic flow is accomplished by employing a polycationic surfactant (Hexadimethrine Bromide), which is added to the background electrolyte. To further improve the resolution of specific carbohydrates, acetone is used as organic modifier. A practical application of the developed method for the fast determination of fructose, glucose, and sucrose in various soft drinks is provided.
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Determination of inorganic anions in Kraft pulping liquors by capillary electrophoresis
Hrc-journal of High Resolution Chromatography, 1996Co-Authors: Sonja M. Masselter, Andreas Zemann, Günther K. BonnAbstract:Various sulfur containing anions (sulfate, sulfite, and thiosulfate) in Kraft pulping process liquors are determined by capillary electrophoresis. In addition, other inorganic anions (hydroxide, chloride, oxalate, carbonate) are analyzed with the developed method. Through optimization of the separation conditions it is possible to simultaneously determine these anionic species in pulping liquors with direct and indirect UV detection at 185, 214, and 254 nm. To ensure short separation times a migration of the anionic analytes in the same direction as the electroosmotic flow (co-electroosmotic CE) is established by reversal of the electroosmotic flow with 1,5-dimethyl-1,5-diazaundecamethylene polymethoBromide (Hexadimethrine Bromide; HDB; polybrene™) which is added to the electrolyte as EOF modifier. The impact of acetonitrile as organic modifier to improve the selectivity of the anionic analytes is also investigated. The developed method is then applied to analyze and quantify various anions in pulping liquors (white and black liquors). By simultaneously determining the hydroxide concentration it is possible to calculate effective alkalinity and sulfidity with the measured concentrations without the need of volumetric methods.
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Influence of organic solvents in coelectroosmotic capillary electrophoresis of phenols
Analytical Chemistry, 1995Co-Authors: Sonja M. Masselter, Andreas ZemannAbstract:The addition of organic solvents (methanol, ethanol, 1-propanol, 2-propanol, acetonitrile) as modifiers in capillary electrophoresis (CE) significantly improves peak shapes and enables the separation of positional isomers of substituted phenols. A reversal of the electroosmotic flow (EOF) to reduce analysis time by migration of the anionic analytes in the same direction as the electroosmotic flow (coelectroosmotic CE) is achieved by using cetyltrimethylammonium Bromide and 1,5-dimethyl-1,5-diazaundecamethylene polymethoBromide (Hexadimethrine Bromide, HDB, Polyrene) as EOF modifiers. The influence of various organic modifiers on EOF, electrophoretic mobilities of the analytes, and theoretical plate numbers is investigated. A high pH value of the buffer electrolytes above the pK A value of the phenols is chosen. The impact of various organic mothers and the influence of the chain length of the alcohols on the separation behavior of alkyl phenols is investigated
Peter J. Oefner - One of the best experts on this subject based on the ideXlab platform.
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Surface-charge reversed capillary zone electrophoresis of inorganic and organic anions.
Electrophoresis, 1995Co-Authors: Peter J. OefnerAbstract:Anions commonly found in biological fluids such as chloride, citrate, phosphate, bicarbonate, lactate, aspartate and glutamate, were determined within 60 s by means of capillary zone electrophoresis and indirect UV detection using 10 mM of chromate, pH 8.0, as both carrier electrolyte and chromophore. The lower mass detection limit was 0.5 pmol. In order to avoid a gradual shift of the pH and, in consequence, drifting ionic mobilities due to the formation of hydroxyl ions at the cathode, 1 mM of 5,5-diethylbarbiturate was added to the background electrolyte. Moreover, fused silica capillaries were coated with a 0.0003% solution of Hexadimethrine Bromide for two minutes between runs to reverse electroendosmotic flow which otherwise would counteract the electrophoretic migration of the anions and, hence, increase time of analysis. It is concluded that charge-reversed capillary zone electrophoresis in concert with indirect UV detection is superior to ion chromatography and conductivity detection in the determination of inorganic and organic anions in biological fluids both with regard to selectivity, sensitivity and speed of analysis1 .
Yuan-hong Wang - One of the best experts on this subject based on the ideXlab platform.
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Separation and Determination of Carbohydrates in Food Samples by Capillary Electrophoresis Using Dynamically Coating the Capillary with Indirect UV Detection
Food Analytical Methods, 2015Co-Authors: Ting-fu Jiang, Lei Chong, Mei-e Yue, Yuan-hong WangAbstract:In this study, the separation and determination of carbohydrates in food samples were developed by capillary electrophoresis using dynamically coating the capillary with indirect UV detection. The polycationic polymers of Hexadimethrine Bromide (HDB) were used as electroosmotic flow (EOF) modifier to reverse the EOF. A highly alkaline pH condition was used in order to charge every carbohydrate negatively. Several important parameters influencing buffer concentration, pH, and HDB concentration were optimized. The optimal background electrolyte composed of 20 mmol L−1 sorbic acid, 0.005 % (w/v) HDB, and 40 mmol L−1 NaOH at pH 12.2. Under optimal conditions, 32 carbohydrates including mono-, di-, oligosaccharides, and sugar alcohols were separated in less than 12 min. The proposed method provided a good linearity, low limits of detection, and good repeatability of the carbohydrates. This method was then utilized to analyze carbohydrates in food samples. The results indicated that the developed method is an excellent alternative for the carbohydrate routine analysis in the food field.
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Separation of Plant Hormones from Biofertilizer by Capillary Electrophoresis Using a Capillary Coated Dynamically with Polycationic Polymers
Analytical sciences : the international journal of the Japan Society for Analytical Chemistry, 2006Co-Authors: Ting-fu Jiang, Yuan-hong Wang, Mei-e YueAbstract:A new, simple and rapid capillary electrophoresis (CE) method, using Hexadimethrine Bromide (HDB) as electroosmotic flow (EOF) modifier, was developed for the identification and quantitative determination of four plant hormones, including gibberellin A3 (GA3), indole-3-acetic acid (IAA), α-naphthaleneacetic acid (NAA) and 4-chlorophenoxyacetic acid (4-CA). The optimum separation was achieved with 20 mM borate buffer at pH 10.00 containing 0.005% (w/v) of HDB. The applied voltage was -25 kV and the capillary temperature was kept constant at 25°C. Salicylic acid was used as internal standard for quantification. The calibration dependencies exhibited good linearity within the ratios of the concentrations of standard samples and internal standard and the ratios of the peak areas of samples and internal standard. The correlation coefficients were from 0.9952 to 0.9997. The relative standard deviations of migration times and peak areas were < 1.93 and 6.84%, respectively. The effects of buffer pH, the concentration of HDB and the voltage on the resolution were studied systematically. By this method, the contents of plant hormone in biofertilizer were successfully determined within 7 min, with satisfactory repeatability and recovery.