Biomedical subjects

Zhide Hu

Publications and source records attributed to Zhide Hu.

At least 37 records · Page 2Linked to original sources

PubMed2005

Study on the binding of Arsenazo-TB to human serum albumin by Rayleigh light scattering technique and FT-IR.

The interaction between Arsenazo-TB and human serum albumin (HSA) was studied by Rayleigh light scattering (RLS) technique and Fourier transformed IR (FT-IR). The binding parameters of Arsenazo-TB with HSA were studied at different temperature of 288, 298, 308, 318 K under the optimum conditions. It is indicated by the Scatchard plots that the binding constant K decreased from 5.03 x 10(7) to 7.13 x 10(6) and the maximum binding number N reduced from 53 to 36 with the increasing of the temperature. The binding process was exothermic, enthalpy driven and spontaneous, as indicated by the thermodynamic analyses, and the major part of the binding energy is hydrophobic interaction. The free energy change deltaG0, the enthalpy change deltaH0 and the entropy change deltaS0 of 288 K were calculated to be -42.46 kJ/mol, -49.17 kJ/mol and 318.15 J/mol K, respectively. The alterations of protein secondary structure in the presence of Arsenazo-TB in aqueous solution were quantitatively calculated from FT-IR spectroscopy with reductions of alpha-helix from 57% to 40% and with increases of beta-sheet from 36% to 39%, beta-turn from 7% to 21%.

Arsenazo III↗

PubMed2005

Quantitative structure-activity relationship models for prediction of sensory irritants (logRD50) of volatile organic chemicals.

Quantitative classification and regression models for prediction of sensory irritants (logRD50) of volatile organic chemicals (VOCs) have been developed. Each compound was represented by the calculated structural descriptors to encode constitutional, topological, geometrical, electrostatic, and quantum-chemical features. The heuristic method (HM) was then used to search the descriptor space and select the descriptors responsible for activity. The best classification results were found using support vector machine (SVM): the accuracy for training, test and overall data set is 96.5%, 85.7% and 94.4%, respectively. The nonlinear regression models were built by radial basis function neural networks (RNFNN) and SVM, respectively. The root mean squared errors (RMS) in prediction for the training, test and overall data set are 0.4755, 0.6322 and 0.5009 for reactive group, 0.2430, 0.4798 and 0.3064 for nonreactive group by RBFNN. The comparative results obtained by SVM are 0.4415, 0.7430 and 0.5140 for reactive group, 0.3920, 0.4520 and 0.4050 for nonreactive group, respectively. This paper proposes an effective method for poisonous chemicals screening and considering.

Irritants↗

PubMed2005

Rapid and ultrasensitive determination of ephedrine and pseudoephedrine derivatizated with 5-(4,6-dichloro-s-triazin-2-ylamino) fluorescein by micellar electrokinetic chromatography with laser-induced fluorescence detection.

This paper presents a micellar electrokinetic chromatography method with laser-induced fluorescence detection to analyze ephedrine (E) and pseudoephedrine (PE) after derivatizated with 5-(4,6-dichloro-s-triazin-2-ylamino) fluorescein. The optimum derivatization conditions were: 0.05 M Na2CO(3/NaHCO3 (pH 9.5), reaction time 30 min at 45 degrees C, molar ratio of DTAF to E and PE mixture 20:1. The baseline separation was achieved within 8 min with running buffer composed of 20 mM borate+20 mM SDS+15% acetonitrile (v/v) (adjusted pH 9.8), and applied voltage of 20 kV. Good linearity relationships (correlation coefficients: 0.9906 for E and 0.9941 for PE) between the peak heights and concentration of the analytes were obtained (2.5-50 ngmL(-1)). The detection limits for E and PE were 3.85 x 10(-4) and 1.41 x 10(-4)ngmL(-1), respectively, which indicated that the proposed method surpassed other chromatographic alternatives in terms of limit of detection by at least 10(3) folds. The method was applied to the analysis of the two alkaloids in ephedra herb plants and its preparations with recoveries in the range of 89.6-107.0%.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2005

Human serum albumin interaction with formononetin studied using fluorescence anisotropy, FT-IR spectroscopy, and molecular modeling methods.

Interaction of formononetin with a model transport protein, human serum albumin (HSA), has been studied using fluorescence anisotropy, FT-IR spectroscopy, and molecular modeling methods. Upon binding with HSA, the fluorescence spectrum of formononetin exhibits appreciable hypsochromic shift along with an enhancement in the fluorescence intensity. Gradual addition of HSA led to a marked increase in fluorescence anisotropy (r). From the value of fluorescence anisotropy, it is argued that the drug is located in a restricted environment of protein. The binding constant (K approximately 1.6 x 10(5) M(-1)) and the standard free energy change (DeltaG(0) approximately -29.9 kJ/mol) of formononetin-HSA interaction have been calculated according to the relevant fluorescence data. Fourier transform infrared measurements have shown that the secondary structures of the protein have been changed by the interaction of formononetin with HSA. Computational mapping of the possible binding sites of formononetin revealed the molecule to be bound in the large hydrophobic cavity of subdomain IIA.

Anisotropy↗

PubMed2005

Accurate quantitative structure-property relationship model to predict the solubility of C60 in various solvents based on a novel approach using a least-squares support vector machine.

A least-squares support vector machine (LSSVM) was used for the first time as a novel machine-learning technique for the prediction of the solubility of C60 in a large number of diverse solvents using calculated molecular descriptors from the molecular structure alone and on the basis of the software CODESSA as inputs. The heuristic method of CODESSA was used to select the correlated descriptors and build the linear model. Both the linear and the nonlinear models can give very satisfactory prediction results: the square of the correlation coefficient R(2) was 0.892 and 0.903, and the root-mean-square error was 0.126 and 0.116, respectively, for the whole data set. The prediction result of the LSSVM model is better than that obtained by the heuristic method and the reference, which proved LSSVM was a useful tool in the prediction of the solubility of C60. In addition, this paper provided a new and effective method for predicting the solubility of C60 from its structures and gave some insight into the structural features related to the solubility of C60 in different solvents.

Electrochemistry↗

PubMed2005

Binding of wogonin to human gammaglobulin.

The binding of wogonin to HGG was studied by spectroscopic method including circular dichroism (CD), fourier transformation infrared spectra (FT-IR), fluorescence spectra. The binding parameters and the thermodynamic parameters for the reaction have been calculated according to Sips method and Gibbs-Helmholtz equation, respectively, at different temperatures. AutoDock3.05 program was used to calculate the interaction modes between the drug and HGG. The Sips plots indicated that the binding of HGG to wogonin at 297, 304, 310 and 317 K is characterized by two binding sites with the average affinity constant Ko at 2.102x10(4), 2.078x10(4), 1.956x10(4) and 1.931x10(4), respectively. The binding process was exothermic, spontaneous and entropy driven, as indicated by the thermodynamic analyses, and the major part of binding energy is electrostatic interaction accompanied by hydrophobic interaction and hydrogen bond. The secondary structure compositions of free HGG and its wogonin complexes were estimated by the FT-IR spectra and the curve-fitted results of amide I band, which are in good agreement with the analyses of CD spectra. Furthermore, the average binding distance between wogonin and HGG (5.60 nm) was obtained on the basis of the theory of Förster energy transfer.

Binding Sites↗

PubMed2005

The accurate QSPR models to predict the bioconcentration factors of nonionic organic compounds based on the heuristic method and support vector machine.

The heuristic method (HM) and support vector machine (SVM) were used to build the linear and nonlinear quantitive structure-property relationship (QSPR) models for the prediction of the fish bioconcentration factors (BCF) for 122 diverse nonionic organic chemicals using the three descriptors calculated from the molecular structure alone and selected by HM. Both the linear and nonlinear model can give very satisfactory prediction results: the square of correlation coefficient R(2) was 0.929 and 0.953, the root mean square (RMS) error was 0.404 and 0.331, respectively for the whole dataset. The prediction result of the SVM model is better than that obtained by heuristic method, which proved SVM was a useful tool in the prediction of the BCF. At the same time, the HM model showed the influencing degree of different molecular descriptors on bioconcentration factors and then could improve the understanding for the bioconcentration mechanism of organic pollutants from molecular level.

Animals↗

PubMed2005

Separation and determination of tetrandrine and fangchinoline in herbal medicines by flow injection-micellar electrokinetic capillary chromatography with internal standard method.

A simple, rapid and precision flow injection-micellar electrokinetic capillary chromatography (FI-MEKC) system with trimethoprim as internal standard (IS) for automated quantitative analysis of tetrandrine (TET) and fangchinoline (FAN) in various herbal medicines was demonstrated. The real sample throughput was 19-40 samples per hour using the background electrolyte (BGE) containing 15mM acetic acid-15mM sodium acetate-3% (v/v) polyoxyethylene sorbitan monolaurate (Tween 20)-5% (v/v) methanol at pH 5.5. The method resulted in excellent linearity, with correlation coefficient of regression equation of 0.9996 and 0.9991 for TET and FAN, respectively. Recoveries were in the range 95-109% and 92-106% for TET and FAN, respectively.

Alkaloids↗

PubMed2005

Separation and simultaneous determination of rutin, puerarin, daidzein, esculin and esculetin in medicinal preparations by non-aqueous capillary.

A simple method for the simultaneous determination of five bioactive components (rutin, puerarin, daidzein esculin and esculetin) in traditional medicinal preparations by non-aqueous capillary electrophoresis with UV detection has been developed for the first time. A running buffer composed of 15% acetonitrile, 2.5% acetic acid and 90 mM sodium cholate in methanol was found to be the most suitable for this separation. The limits of detection for five analytes were over the range of 0.050-1.216 microg ml(-1). The relative standard deviations (R.S.Ds.) of the migration times and the peak areas of the analytes were in the range of 1.3-2.9% and 2.2-2.7% (intraday), 1.7-1.9% and 2.8-3.6% (interday), respectively. In the tested concentration range, linear relationships (correlation coefficients: 0.9974 for rutin, 0.9976 for puerarin, 0.9981 for daidzein, 0.9972 for esculin and 0.9929 for esculetin) between peak areas and concentrations of the analytes were obtained. This method has been successfully applied to simultaneous determination of the five bioactive components with recoveries over the range of 89.4-107.4%.

Electrophoresis, Capillary↗

PubMed2005

Prediction of pK(a) for neutral and basic drugs based on radial basis function Neural networks and the heuristic method.

PURPOSES: Quantitative structure-property relationships (QSPR) were developed to predict the pK(a) values of a set of neutral and basic drugs via linear and nonlinear methods. The ability of the models to predict pK(a) was assessed and compared. METHODS: The descriptors of 74 neutral and basic drugs in this study were calculated by the software CODESSA, which can calculate constitutional, topological, geometrical, electrostatic, and quantum chemical descriptors. Linear and nonlinear QSPR models were developed based on the heuristic method (HM) and radial basis function neural networks (RBFNN), respectively. The heuristic method was also used for the preselection of appropriate molecular descriptors. RESULTS: The obtained linear model had a correlation coefficient of r=0.884, F=37.72 with a root-mean-squared (RMS) error of 0.482 for the training set, and r=0.693, F=11.99, nd RMS=0.987 for the test set. The RMS in predicting the overall data set is 0.619. The nonlinear model gave better results; for the training set, r=0.886, F=202.314, and RMS=0.458, and for the test set r=0.737, F=15.41, and RMS=0.613. The RMS error in prediction for overall data set is 0.493. Prediction results from nonlinear model are in good agreement with experimental values. CONCLUSIONS: In present study, we developed a QSPR model to predict the important parameter (pK(a)) of neutral and basic drugs. The model is useful in predicting pK(a) during the discovery of new drugs when experimental data are unknown.

Neural Networks, Computer↗

PubMed2005

Novel and simple nonaqueous capillary electrophoresis separation and determination bioactive triterpenes in Chinese herbs.

Three bioactive triterpenes ursolic acid, oleanolic acid and 2alpha,3beta,24-trihydroxy-urs-12-en-28-oic acid were simultaneously separated by nonaqueous capillary electrophoresis (NACE) with methanol:acetonitrile (65:35 v/v) mixture containing 90 mm trishydroxymethylaminomethane (Tris) at an applied voltage of +25 kV and a hydrodynamic injection of 5s. The effect of solvent composition, electrolyte nature and concentration on the electrophoretic behavior of the analytes were systematically studied. Separations were carried out in a fused-silica capillary tube with UV detection at 214 nm. Good separation and correlation coefficients were obtained. Meanwhile, the method was applied to separation and determination the three components in six Chinese herbs extraction. It is concluded that this method could be used for speedy and accurate qualitative and quantitative analysis of bioactive triterpenes in Chinese herbs.

Acetonitriles↗

PubMed2005

Separation and determination of lignans from seeds of Schisandra species by micellar electrokinetic capillary chromatography using ionic liquid as modifier.

In this paper, a micellar electrokinetic chromatographic (MEKC) method using ionic liquid as modifier for the quantification of the active components of lignans found in the medicinal herbs Schisandra species was developed for the first time. Preliminary investigations employing sodium dodecyl sulfate (SDS) as surfactant did not lead to the necessary resolution of the studied compounds, the addition of ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4) to the SDS micellar system resulted in the complete separation of all the compounds. The effects on the separation by several parameters such as BMIM-BF4 and SDS concentration, applied voltage, background electrolyte pH and concentration, were evaluated. Under the optimal conditions (5 mM borate-5 mM phosphate buffer in the presence of 20 mM SDS and 10 mM BMIM-BF4, pH 9.2, applied voltage 25 kV and detection at 254 nm), the method successfully applied to the determination of lignans in extracts of Schisandra chinensis (Turcz.) Baill. and Schisandra henryi C.B. Clarke in less than 13 min. The separation mechanism was also discussed.

Borates↗

PubMed2005

Method for on-line derivatization and separation of aspartic acid enantiomer in pharmaceuticals application by the coupling of flow injection with micellar electrokinetic chromatography.

A novel, easy and accurate capillary electrophoresis (CE) coupled with flow injection (FI) method for the separation and determination of aspartic acid (Asp) enantiomers by on-line derivatization had been developed, and it had been applied to the real sample for the first time. The derivatization reagents were o-phthalaldehyde (OPA) and mercaptoethanol (ME), which were obtained easily, the chiral selector was beta-cyclodextrin (beta-CD), the micellar chemical was sodium dodecyl sulfate (SDS), and the modifier was methanol. By on-line derivatization, aspartic acid enantiomers were automatically and reproducibly converted to the ultraviolet (UV)-absorbing diastereoisomer derivates, which were separated by micellar electrokinetic chromatography (MEKC). According to the factors affecting the separation and sensitivity of aspartic acid enantiomer and other amino acids in the real sample, the pH value and concentration of the buffer, the concentration of beta-CD and SDS, the volume percentage of the methanol (v/v) in the buffer, the applied voltage and the conversion time were selected as the investigating variates. Under the investigated separation conditions, D-aspartic acid (D-Asp), L-aspartic acid (L-Asp) and other four amino acids achieved the baseline separation in not only the standard mixture of amino acids but also the real sample (Compound Amino Acid Injection (6AA)). The repeatability (defined as relative standard deviation (RSD), n = 5) was 4.0% and 4.0% with peak area evaluation, and 4.2% and 3.7% with peak height evaluation for D-Asp and L-Asp in the real sample. Recovery at added standard levels of 1.0, 3.0 and 6.0 mM was 92%, 104% and 109%, respectively.

Aspartic Acid↗

PubMed2005

Interaction of wogonin with bovine serum albumin.

The binding of wogonin with bovine serum albumin (BSA) was investigated at different temperatures by fluorescence, circular dichroism (CD) and Fourier transform infrared spectroscopy (FT-IR) at pH7.40. The association constants K were determined by Stern-Volmer equation based on the quenching of the fluorescence of BSA in the presence of wogonin, which were in agreement with the constants calculated by Scatchard plots. The thermodynamic parameters were calculated according to the Van't Hoff equation and the result indicated that DeltaH(0) and DeltaS(0) had a negative value (-12.02 kJ/mol) and a positive value (58.72 J/mol K), respectively. On the basis of the displacement experimental and the thermodynamic results, it is considered that wogonin binds to site I (subdomain IIA) of BSA mainly by hydrophobic interaction. The studied results by FT-IR and CD experiment indicated that the secondary structures of protein have been perturbed by the interaction of wogonin with BSA.

Animals↗

PubMed2005

Support vector machine and the heuristic method to predict the solubility of hydrocarbons in electrolyte.

A new method support vector machine (SVM) and the heuristic method (HM) were used to develop nonlinear and linear models between the solubility in electrolyte containing sodium chloride and three molecular descriptors of 217 nonelectrolytes. The molecular descriptors representing the structural features of the compounds include two topological and one electrostatic descriptor. The three molecular descriptors selected by HM in CODESSA were used as inputs for SVM. The results obtained by HM and SVM both were satisfactory. The model of HM leads to a correlation coefficient (R) of 0.980 and root-mean-square error (RMS) of 0.219 for the test set. The same descriptors were also employed to build the model in pure water, and the prediction results were consistent with the experimental solubilities. Furthermore, a predictive correlation coefficient R = 0.988 and RMS error of 0.170 for the test set were obtained by SVM. The prediction results are in very good agreement with the experimental values. This paper provides a new and effective method for predicting the solubility in electrolyte and reveals some insight into the structural features that are related to the noneletrolytes.

Journal Article↗

PubMed2005

Separation and determination of pseudoephedrine, dextromethorphan, diphenhydramine and chlorpheniramine in cold medicines by nonaqueous capillary electrophoresis.

An easy, rapid and simple nonaqueous capillary electrophoresis (NACE) method was developed for the identification and determination of four basic nitrogenous compounds, i.e. pseudoephedrine (PE), dextromethorphan (DXM), diphenhydramine (DHM) and chlorpheniramine (CLP). The most suitable running buffer was composed of 40 mM ammonium acetate, 10% acetonitrile (ACN) in methanol with a fused-silica capillary column (47 cm x 75 microm i.d.), 25 kV applied voltage and 25 degrees C capillary temperature. The calibration curves revealed linear relationships between the peak area for each analyte and its concentration (correlation coefficients: 0.9993 for PE, 0.9971 for DXM, 0.9991 for DHM, and 0.9995 for CLP, respectively). The relative standard deviations of the migration time and peak area of the four compounds were 0.37, 3.90, 0.73 and 0.68, and 2.80, 3.50, 1.60 and 3.70%, respectively. The method was successfully applied to determine the four compounds in five cold medicines, the recoveries of the four constituents ranging between 91 and 109%.

Chlorpheniramine↗

PubMed2005

Effect of Chinese medicine alpinetin on the structure of human serum albumin.

Alpinetin (7-hydroxy-5-methoxyflavanone), one of the main constituents from the seeds of Alpinia katsumadai Hayata, belongs to flavonoids with its usefulness as antibacterial, anti-inflammatory and other important therapeutic activities of significant potency and low systemic toxicity. In this paper, the interaction of alpinetin to human serum albumin (HSA) has been studied for the first time by spectroscopic method including Fourier transform infrared (FT-IR) spectroscopy, circular dichroism (CD), and UV-absorption spectroscopy in combination with fluorescence quenching study under physiological conditions with drug concentrations of 3.3 x 10(-6)-2.0 x 10(-5)mol/L. The results of spectroscopic measurements and the thermodynamic parameters obtained (the enthalpy change DeltaH(0) and the entropy change DeltaS(0) were calculated to be -10.20 kJ/mol and 53.97 J/molK(-1) according to the Van't Hoff equation) suggest that hydrophobic interaction is the predominant intermolecular forces stabilizing the complex, which is also good agreement with the results of molecule modeling study. The alterations of protein secondary structure in the presence of alpinetin in aqueous solution were quantitatively estimated by the evidences from FT-IR and CD spectroscopy with reductions of alpha-helices about 24%, decreases of beta-sheet structure about 2%, and increases of beta-turn structure about 21%. The quenching mechanism and the number of binding site (n approximately 1) were obtained by fluorescence titration data. Fluorescent displacement measurements confirmed that alpinetin bind HSA on site III. In addition, the effects of common ions on the constants of alpinetin-HSA complex were also discussed.

Binding Sites↗

PubMed2005

Application of non-aqueous micellar electrokinetic chromatography to the analysis of active components in radix Salviae miltiorrhizae and its medicinal preparations.

A simple, economical and effective non-aqueous micellar electrokinetic chromatography (NAMEKC) method was developed for simultaneous assay of three bioactive components (cryptotanshinone, tanshinone IIA and tanshinone I) in radix Salviae miltiorrhizae and its medicinal preparations for the first time. After optimization of separation conditions, a buffer of 140 mmol l(-1) sodium cholate (SC) in methanol was selected for the separation of the three tanshinones, but baseline separation of tanshinone I and tanshinone IIA in practical samples was not achieved. Therefore, second-order derivative electropherograms were applied for resolving overlapping peaks. Regression equations revealed good linear relationships (correlation coefficients 0.995-0.999) between peak heights in second-order derivative electropherograms and concentrations of the three analytes. The recoveries of three constituents ranged from 91.3 to 105.7%. The results indicated that baseline separation of the analytes was hard to be achieved in practical samples sometimes and second-order derivative electropherograms was applicable for the resolving and analysis of overlapping peaks.

Chemical Phenomena↗