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ABSTRACT: An efficient and durable on-line capillary immobilized trypsin microreactor was successfully established to study the enzyme kinetics and screen its inhibitors from natural extracts through capillary electrophoresis (CE). In this procedure, trypsin was immobilized on the inner wall at the inlet of the capillary treated with 3-aminopropyl-trimethoxy silane (3-APTS), producing trypsin microreactor via cross-linking of glutaraldehyde with 3-APTS and trypsin. The rest of the capillary was selected as a channel for separating the generated product and unreacted substrate of trypsin enzymatic reaction. The parameters affecting the separation efficiency and activity of immobilized trypsin were evaluated systematically. The optimized conditions were as follows: 50 mM Tris-HCl (pH=8.0), 15 kV, 37 °C, 10 mM substrate, incubation for 2 min. Under optimal conditions, separation of the product and substrate was achieved through CE within 3.5 min. The obtained results of Michaelis constant (Km), inhibition kinetics constant (Ki), and half maximal inhibitory concentration (IC50) for the immobilized trypsin using benzamidine hydrochloride hydrate as a model inhibitor were 1.56 mM, 1.79 mM, and 3.98 mM, respectively. The proposed method was successfully applied for screening of trypsin inhibitors from 19 kinds of natural extracts.
Analytical Biochemistry 03/2013; · 3.00 Impact Factor
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ABSTRACT: The mechanism of interaction between deoxynivalenol (DON) and human serum albumin (HSA) was studied using spectroscopic methods including fluorescence spectra, UV-VIS, Fourier transform infrared (FT-IR) and circular dichroism (CD). The quenching mechanism was investigated in terms of the association constants, number of binding sites and basic thermodynamic parameters. The distance between the HSA donor and the acceptor DON was 2.80 nm as derived from fluorescence resonance energy transfer. The secondary structure compositions of free HSA and its DON complexes were estimated by the FT-IR spectra. Alteration of the secondary protein structure in the presence of DON was confirmed by UV-VIS and CD spectroscopy. Molecular modelling revealed that a DON-protein complex was stabilised by hydrophobic forces and hydrogen bonding. It was potentially useful for elucidating the toxigenicity of DON when combined with biomolecular function effect, transmembrane transport, toxicological testing and the other experiments.
Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment 12/2012;
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ABSTRACT: In this study we developed a simple capillary electrophoresis (CE) method with an on-line acetylcholinesterase (AChE) microreactor at the inlet of capillary for inhibitor screening. The fused-silica capillary surface was modified with a polycationic polyethylenimine coating. Solutions of the enzyme and chitosan were then injected to immobilize the enzyme in approximately 2.9 cm of the capillary inlet (total length of capillary 60.2 cm) by electrostatic interaction and the film overlay technique. Separation of enzyme reaction product (thiocholine, ThCh) and unreacted substrate (acetylthiocholine, AThCh) was achieved within 3.0 min. The conditions affecting the efficiency of reaction of the enzyme were optimized by measuring the peak area of ThCh. Under the optimum conditions, using Huperzine-A as model inhibitor, K (i) and IC (50) were 0.551 μmol L(-1) and 1.52 μmol L(-1), respectively, for immobilized AChE. Finally, screening of a small compound library containing two known AChE inhibitors and 30 natural extracts was conducted, and species with inhibition activity were directly identified. Compared with previous publications on screening for AChE inhibitors in natural products based on CE methods, the method developed in this work has the advantages of lower cost per analysis, less leakage, and better bioaffinity for the immobilized enzyme because of the unique properties of sodium alginate and chitosan.
Analytical and Bioanalytical Chemistry 08/2012; 404(8):2397-405. · 3.78 Impact Factor
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ABSTRACT: Liensinine (LIE), isoliensinine (ISO) and neferine (NEF) from embryo of the seed of Nelumbo nucifera Gaertn were first separated and quantitatively analyzed by micellar electrokinetic chromatography with internal standard
(IS) using a cationic surfactant, tetradecyltrimethyl ammonium bromide (TTAB). Complete separation of the analytes was optimally
achieved within 15min using 40mM sodium dihydrogenphosphate (pH 6.40) containing 10mM TTAB and 15% (v/v) methanol as buffer. Tetrahydropalmatine was used as IS to improve the repeatability and linearity relativity. The IS method
resulted in excellent linearity, with correlation coefficients of regression equations of 0.9997, 0.9997 and 0.9992 for LIE,
ISO and NEF, respectively. Finally, two sample extraction methods were used to investigate the contents of different parts
of the embryos.
KeywordsMicellar electrokinetic chromatography–Cationic surfactant–Bisbenzylisoquinoline alkaloids
Chromatographia 04/2012; 73(5):535-540. · 1.20 Impact Factor
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ABSTRACT: A new capillary electrophoresis procedure with field-enhanced stacking concentration for the analysis of umbelliferone, rutin
and aesculetin in Prunella vulgaris is established for the first time. After optimization of the separation and concentration conditions, the three analytes
can be separated within 6min and quantified with high sensitivity. The method was useful for qualitative and quantitative
analysis of umbelliferone, rutin and aesculetin in Prunella vulgaris with recovery of 97.5 to 105.3%.
Chromatographia 04/2012; 70(11):1733-1736. · 1.20 Impact Factor
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ABSTRACT: Models to predict binding constant (logK) to bovine serum albumin (BSA) should be very useful in the pharmaceutical industry to help speed up the design of new compounds,
especially as far as pharmacokinetics is concerned. We present here an extensive list of logK binding constants for thirty-five compounds to BSA determined by florescence quenching from the literature. These data have
allowed us the derivation of a quantitative structure-property relationship (QSPR) model to predict binding constants to BSA
of compounds on the basis of their structure. A stepwise multiple linear regression (MLR) was performed to build the model.
The statistical parameter provided by the MLR model (R = 0.9200, RMS = 0.3305) indicated satisfactory stability and predictive
ability for the model. Using florescence quenching spectroscopy, we also experimentally determined the binding constants to
BSA for two bioactive components in traditional Chinese medicines. Using the proposed model it was possible to predict the
binding constants for each, which were in good agreement with the experimental results. This QSPR approach can contribute
to a better understanding of structural factors of the compounds responsible for drug-protein interactions, and be useful
in predicting the binding constants of other compounds.
Central European Journal of Chemistry 04/2012; 7(1):59-65. · 1.07 Impact Factor
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ABSTRACT: A methodology based on the coupling of experimental design and artificial neural networks (ANNs) is proposed in the optimization
of a new flow injection system for the spectrophotometric determination of Al(III) with Arsenazo DBM, which has for the first
time been used as chromogenic reagent in the quantitative analysis of aluminium. An orthogonal design is utilized to design
the experimental protocol, in which three variables are varied simultaneously. Feedforward-type neural networks with faster
back propagation (BP) algorithm are applied to model the system, and then optimization of the experimental conditions is carried
out in the neural network with 3-7-1 structure, which have been confirmed to be able to provide the maximum performance. In
contrast to traditional methods, the use of this methodology has advantages in terms of a reduction in analysis time and an
improvement in the ability of optimization. The method has been applied to the determination of Al(III) in steel samples and
provided satisfactory results.
Fresenius Journal of Analytical Chemistry 04/2012; 366(1):17-21.
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ABSTRACT: A new method is proposed for the spectrophotometric determination of Pd(II), based on the reaction of Pd(II) with 2-(4-chloro-2-phosphonophenylazo)-7-(3-carboxyphenylazo)-1,8-dihydroxynaphthalene-3,6-disulfonic
acid(CPA-mK) in sulfuric acid without heating. Beer’s law is obeyed for 1.0–4.0 μg of Pd (II) in 10 mL of solution. The calibration
curve from 1.0 to 42.0 μg in 10 mL of solution is modeled successfully by artificial neural networks (ANNs). The maximum relative
error between experimental values and the values predicted by ANNs is 1.5%. In comparison with some mathematical functions,
ANNs show better ability for curve fitting, thus greatly extending the applicable range of the calibration curve of this new
system. The method has been applied to determine Pd (II) in ore and catalyst samples with a relative error of less than 4%
and with a recovery range between 94% and 103%.
Fresenius Journal of Analytical Chemistry 04/2012; 367(3):215-219.
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ABSTRACT: A micellar electrokinetic chromatography method was developed for the simultaneous determination of dopamine, epinephrine A micellar electrokinetic chromatography method was developed for the simultaneous determination of dopamine, epinephrine
and 5-hydroxytryptamine. Several experimental parameters such as surfactant type and concentration, buffer concentration and and 5-hydroxytryptamine. Several experimental parameters such as surfactant type and concentration, buffer concentration and
pH, type and concentration of organic modifier were evaluated for the analysis of the studied compounds. Among the investigated pH, type and concentration of organic modifier were evaluated for the analysis of the studied compounds. Among the investigated
separation conditions, the composition of micelles, pH and the methanol concentration were the critical parameters. Dopamine, separation conditions, the composition of micelles, pH and the methanol concentration were the critical parameters. Dopamine,
epinephrine and 5-hydroxytryptamine were separated and determined successfully within 7.5min in Toad venom and Common yam epinephrine and 5-hydroxytryptamine were separated and determined successfully within 7.5min in Toad venom and Common yam
rhizome under the optimum conditions. rhizome under the optimum conditions.
Chromatographia 04/2012; 70(9):1467-1471. · 1.20 Impact Factor
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ABSTRACT: A novel method of on-line single drop microextraction (SDME) coupled with sweeping micellar electrokinetic chromatography (MEKC) for the selective extraction and dual preconcentration of alkaloids was developed. In this technique, analytes of three alkaloids were firstly extracted from 4.0 mL basic aqueous sample solution (donor phase, 500 mM NaOH) into a layer of n-octanol at temperature 30 °C with the stirring rate of 1150 rpm, then back-extracted into the acidified aqueous acceptor (acceptor phase, 50 mM H₃PO₄) suspended at the tip of a capillary at 650 rpm. Then, the aqueous acceptor was introduced into capillary by hydrodynamic injection with a height difference of 15 cm between the inlet and outlet of capillary for 300 s, and analyzed directly by on-line sweeping MEKC. With the selective SDME, we were able to extract three alkaloids without any interfering components in human urine samples. Under the optimum conditions, the proposed method achieved limits of detections (LOD) of between 0.2 ng mL⁻¹ and 1.5 ng mL⁻¹ with 1583-3556-fold increases in detection sensitivity for three analytes, which indicated that it was a promising method for analysis of alkaloids in human urine.
Journal of chromatography. A 08/2011; 1218(33):5712-7. · 4.19 Impact Factor
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ABSTRACT: A quantitative model is developed to predict the Km of 47 human dopamine sulfotransferases by gene expression programming. Each kind of compound is represented by several calculated structural descriptors of moment of inertia A, average electrophilic reactivity index for a C atom, relative number of triple bonds, RNCG relative negative charge, HA-dependent HDSA-1, and HBCA H-bonding charged surface area. Eight fitness functions of the gene expression programming method are used to find the best nonlinear model. The best quantitative model with squared standard error and square of correlation coefficient are 0.096 and 0.91 for training data set, and 0.102 and 0.88 for test set, respectively. It is shown that the gene expression programming-predicted results with fitness function are in good agreement with experimental ones.
Chemical Biology & Drug Design 06/2011; 78(3):370-7. · 2.28 Impact Factor
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ABSTRACT: A simple and novel method of single drop liquid-liquid-liquid microextraction (SD-LLLME) coupled with capillary electrophoresis (CE) for the determination of six fluoroquinolones (FQs) was developed. The method was eventually applied to extraction and preconcentration of FQs in human urine samples. Good linear relationships were obtained for all analytes in a range of 40-1000 μg L⁻¹ with the correlation coefficients from 0.9913 to 0.9995. The limit of detections (LODs) varied from 7.4 to 31.5 μg L⁻¹ at a signal-to-noise (S/N) of 3. The recoveries at two spiking levels were 81.8-104.9% with relative standard deviations <8.3%.
Journal of chromatography. B, Analytical technologies in the biomedical and life sciences 02/2011; 879(3-4):291-5. · 2.78 Impact Factor
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ABSTRACT: A simple and novel method of directly suspended droplet microextraction (DSDME) combined with single drop back-extraction prior to capillary electrophoresis (CE) measurement is developed. In this technique, DSDME was firstly carried out under the maximum stirring rate for a desired time. Then, an aqueous droplet as back-extractive phase suspended at the needle tip was immersed in droplet of organic phase for back-extracted. After extraction, the aqueous droplet was transferred into a suitable vial and injected into CE for analysis. Three alkaloids were selected as model compounds for developing and evaluating the method performance. Under the optimum conditions, the enrichment factors ranged from 231 to 524. The relative standard deviations for five replicates were in the range of 4.8-8.1%. The calibration graph was linear in the range of 20-1000 ng mL(-1) yielding correlation coefficients higher than 0.9983. The limit of detections varied from 8.1 to 14.1 ng mL(-1). Human urine samples were spiked with three alkaloids standard to assess the matrix effects and satisfactory results were obtained. The advantages of this method are simplicity of operation, rapid detection, low cost, high enrichment factor and little solvent consumption.
Talanta 02/2011; 83(5):1673-9. · 3.79 Impact Factor
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ABSTRACT: The epidermal growth factor receptor (EGFR) protein tyrosine kinase (PTK) is an important protein target for anti-tumor drug discovery. To identify potential EGFR inhibitors, we conducted a quantitative structure-activity relationship (QSAR) study on the inhibitory activity of a series of quinazoline derivatives against EGFR tyrosine kinase. Two 2D-QSAR models were developed based on the best multi-linear regression (BMLR) and grid-search assisted projection pursuit regression (GS-PPR) methods. The results demonstrate that the inhibitory activity of quinazoline derivatives is strongly correlated with their polarizability, activation energy, mass distribution, connectivity, and branching information. Although the present investigation focused on EGFR, the approach provides a general avenue in the structure-based drug development of different protein receptor inhibitors.
PLoS ONE 01/2011; 6(7):e22367. · 4.09 Impact Factor
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ABSTRACT: A new simple, rapid and sensitive spectrophotometric flow injection analysis (FIA) method is developed for the determination of chromium(VI) based on its reaction with 3,5-Br2-PADAP and SCN°- in a strongly acidic medium. This produces an unstable violet product with a maximum absorption at 605 nm. As the product formed is unstable, FIA is an ideal method to reproducibly monitor the transient signal. The calibration curve is linear over 1.0 × 10–6 to 7.0 × 10–5 mol l–1. The correlation coefficient of the calibration curve is 0.9998, the detection limit is 5.0 × 10–7Cr2O72- mol l–1 and sample throughput is 80 h–1. The method has been successfully applied to the determination of chromium in steel.
Bulletin des Sociétés Chimiques Belges. 08/2010; 104(7):415 - 419.
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ABSTRACT: The feasibility of microwave-accelerated derivatization for capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection was evaluated. The derivatization reaction was performed in a domestic microwave oven. Histidine (His), 1-methylhistidine (1-MH) and 3-methylhistidine (3-MH) were selected as test analytes and fluorescein isothiocyanate (FITC) was chosen as a fluorescent derivatizing reagent. Parameters that may affect the derivatization reaction and/or subsequent CE separation were systematically investigated. Under optimized conditions, the microwave-accelerated derivatization reaction was successfully completed within 150 s, compared to 4-24 h in a conventional water-bath derivatization process. This will remarkably reduce the overall analysis time and increase sample throughput of CE-LIF. The detection limits of this method were found to be 0.023 ng/mL for His, 0.023 ng/mL for 1-MH, and 0.034 ng/mL for 3-MH, respectively, comparable to those obtained using traditional derivatization protocols. The proposed method was characterized in terms of precision, linearity, accuracy and successfully applied for rapid and sensitive determination of these analytes in human urine.
Talanta 06/2010; 82(1):72-7. · 3.79 Impact Factor
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ABSTRACT: For the first time, a new multifunctional nanomaterial which combined the superparamagnetic property of iron oxide nanoparticles with the fluorescent property of morin-Al3+ complex was prepared. Iron oxide nanoparticles were first coated with SiO2 which could isolate them from the complex and the surrounding. Subsequently, Al2O3 . nH2O which provided active aluminum atom were deposited on the silica shell. Finally, morin which would react with the reactive aluminum atom was added into the reaction mixture to prepare the final multifunctional nanomaterial. The obtained product was characterized by X-ray powder diffraction, transmission electron microscopy, fourier transform infrared spectra, photoluminescence spectra, fluorescence microscopy, and vibration sample magnetometer. The characterization results showed that the final samples had an average size of 60 nm with spherical shape. The saturation magnetization of this new synthesized material was about 8.5 emu g(-1). Its excitation and emission wavelengths were 420 and 513 nm, respectively.
Journal of Nanoscience and Nanotechnology 05/2009; 9(4):2664-70. · 1.56 Impact Factor
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ABSTRACT: Derivative spectrophotometry is introduced for the quantification of overlapping peaks in capillary electrophoresis. The application
for resolving overlapping peaks is tested using eleven benzoic acids as examples. Compared with common spectrophotometric
detection, the derivative mode has slightly lower reproducibility, comparable sensitivity but much higher separation efficiency
as the peak is much sharpened. Derivative spectrophotometry offers the advantages of reagent-, time- and labor-saving since
only few optimizations of separation conditions for normal CE are essential to make the peaks partly baseline-resolved. Analysis
of real samples using the method was also performed and results obtained give evidence of the potential for improved quantification
without loss in accuracy.
Microchimica Acta 02/2009; 164(3):487-491. · 3.03 Impact Factor
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ABSTRACT: Cadmium telluride (CdTe) and iron oxide nanoparticles doped silica nanospheres were prepared by a multistep method. Iron oxide nanoparticles were first coated with silica and then modified with amino group. Thereafter, CdTe nanoparticles were assembled on the particle surfaces by their strong interaction with amino group. Finally, an outer silica shell was deposited. The final products were characterized by X-ray powder diffraction, transmission electron microscopy, vibration sample magnetometer, photoluminescence spectra, Fourier transform infrared spectra (FT-IR), and fluorescent microscopy. The characterization results showed that the final nanomaterial possessed a saturation magnetization of about 5.8 emu g(-1) and an emission peak at 588 nm when the excitation wavelength fixed at 380 nm.
Nanoscale Research Letters 01/2009; 4(7):640-645. · 2.73 Impact Factor
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ABSTRACT: A new method for preparing magnetic iron oxide nanoparticles coated by organic dye-doped silica shell was developed in this article. Iron oxide nanoparticles were first coated with dye-impregnated silica shell by the hydrolysis of hexadecyltrimethoxysilane (HTMOS) which produced a hydrophobic core for the entrapment of organic dye molecules. Then, the particles were coated with a hydrophilic shell by the hydrolysis of tetraethylorthosilicate (TEOS), which enabled water dispersal of the resulting nanoparticles. The final product was characterized by X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, photoluminescence spectroscopy, and vibration sample magnetometer. All the characterization results proved the final samples possessed magnetic and fluorescent properties simultaneously. And this new multifunctional nanomaterial possessed high photostability and minimal dye leakage.
Nanoscale Research Letters 12/2008; 3(12):496-501. · 2.73 Impact Factor
