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Guowang Xu

Publications and source records attributed to Guowang Xu.

At least 37 records · Page 2Linked to original sources
PubMed2006

[Metabolite fingerprint and biomarkers identification of rat urine after dosed with ginsenoside Rg3 based on ultra high performance liquid chromatography/time-of-flight mass spectrometry (UPLC/TOF-MS)].

Porous particles of 1.7 microm was employed for ultra high performance liquid chromatography (UPLC), resulting in higher peak capacity, greater resolution and increased sensitivity in comparison with high performance liquid chromatography (HPLC). Time-of-flight mass spectrometer (TOF-MS) with a lockmass interface was used for the structure identification through exact mass and MS/MS experiment. The hyphenation of these two technologies made it a suitable platform for analysis of complex samples and identification of unknown compounds. Ginsenoside Rg3 has been considered as the major active component of Panax ginseng. Effect of the administration of a single dose of the Ginsenoside Rg3 to male Sprague Dawley rats on the urinary metabolite profiles of a range of endogenous metabolites had been investigated using UPLC/TOF-MS. Urine samples were collected from both dosed and control animals. Analysis of these samples revealed marked changes in the pattern of endogenous metabolites due to the effect of Ginsenoside Rg3. Significant disturbances in the urinary metabolite were observed in the first day after dose. Endogenous metabolites with significant up-regulation identified by accurate mass and MS/MS were xanthurenic acid, and kynurenic acid.

Animals↗
PubMed2005

Quantitative determination of compounds in tobacco essential oils by comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometry.

A quantitative analysis of the individual compounds in tobacco essential oils is performed by comprehensive two-dimensional gas chromatography (GC x GC) combined with flame ionization detector (FID). A time-of-flight mass spectrometer (TOF/MS) was coupled to GC x GC for the identification of the resolved peaks. The response of a flame ionization detector to different compound classes was calibrated using multiple internal standards. In total, 172 compounds were identified with good match and 61 compounds with high probability value were reliably quantified. For comparative purposes, the essential oil sample was also quantified by one-dimensional gas chromatography-mass spectrometry (GC/MS) with multiple internal standards method. The results showed that there was close agreement between the two analysis methods when the peak purity and match quality in one-dimensional GC/MS are high enough.

Gas Chromatography-Mass Spectrometry↗
PubMed2005

Deconvolution of overlapped peaks based on the exponentially modified Gaussian model in comprehensive two-dimensional gas chromatography.

Comprehensive two-dimensional gas chromatography (GC x GC) has attracted much attention for the analysis of complex samples. Even with a large peak capacity in GC x GC, peak overlapping is often met. In this paper, a new method was developed to resolve overlapped peaks based on the mass conservation and the exponentially modified Gaussian (EMG) model. Linear relationships between the calculated sigma, tau of primary peaks with the corresponding retention time (tR) were obtained, and the correlation coefficients were over 0.99. Based on such relationships, the elution profile of each compound in overlapped peaks could be simulated, even for the peak never separated on the second-dimension. The proposed method has proven to offer more accurate peak area than the general data processing method.

Chromatography, Gas↗
PubMed2005

Resolution prediction and optimization of temperature programme in comprehensive two-dimensional gas chromatography.

A model is developed for predicting the resolution of interested component pair and calculating the optimum temperature programming condition in the comprehensive two-dimensional gas chromatography (GC x GC). Based on at least three isothermal runs, retention times and the peak widths at half-height on both dimensions are predicted for any kind of linear temperature-programmed run on the first dimension and isothermal runs on the second dimension. The calculation of the optimum temperature programming condition is based on the prediction of the resolution of "difficult-to-separate components" in a given mixture. The resolution of all the neighboring peaks on the first dimension is obtained by the predicted retention time and peak width on the first dimension, the resolution on the second dimension is calculated only for the adjacent components with un-enough resolution on the first dimension and eluted within a same modulation period on the second dimension. The optimum temperature programming condition is acquired when the resolutions of all components of interest by GC x GC separation meet the analytical requirement and the analysis time is the shortest. The validity of the model has been proven by using it to predict and optimize GC x GC temperature programming condition of an alkylpyridine mixture.

Chromatography, Gas↗
PubMed2005

Strategy for metabonomics research based on high-performance liquid chromatography and liquid chromatography coupled with tandem mass spectrometry.

Metabonomics, the study of metabolites and their roles in various disease states, is a novel methodology arising from the post-genomics era. This methodology has been applied in many fields. Current metabonomic practice has relied on mass spectrometry (MS), gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR) to analyze metabolites. In this study, a strategy was developed for applying high-performance liquid chromatography (HPLC) and LC-MS-MS to metabonomics research. One of the key problems to be solved in this strategy is to match the peaks between the chromatograms. A peak alignment algorithm has been developed to match the chromatograms before the pattern recognition. As an application example, the strategy described above was applied to metabonomics research on liver diseases, and the false-positive result of live cancer diagnosis from the hepatocirrhosis and hepatitis diseases was effectively reduced to 7.40%. Based on the pattern recognition, several potential biomarkers were found and further identified by the following LC-MS-MS experiments. The structures of eight potential biomarkers were given for distinguishing the liver cancer from the hepatocirrhosis and hepatitis diseases.

Adult↗
PubMed2005

Plasma phospholipid metabolic profiling and biomarkers of type 2 diabetes mellitus based on high-performance liquid chromatography/electrospray mass spectrometry and multivariate statistical analysis.

Liquid chromatography/mass spectrometry (LC/MS) followed by multivariate statistical analysis has been successfully applied to the plasma phospholipids metabolic profiling in type 2 diabetes mellitus (DM-2). Principal components analysis and partial least-squares discriminant analysis (PLS-DA) models were tested and compared in class separation between the DM2 and control. The application of an orthogonal signal correction filtered model highly improved the class distinction and predictive power of PLS-DA models. Additionally, unit variance scaling was also tested. With this methodology, it was possible not only to differentiate the DM2 from the control but also to discover and identify the potential biomarkers with LC/MS/MS. The proposed method shows that LC/MS combining with multivariate statistical analysis is a complement or an alternative to NMR for metabonomics applications.

Biomarkers↗
PubMed2005

Docosahexaenoic acid changes lipid composition and interleukin-2 receptor signaling in membrane rafts.

Polyunsaturated fatty acids, including docosahexaenoic acid (DHA, 22:6n-3), modulate immune responses and exert beneficial immunosuppressive effects, but the molecular mechanisms inhibiting T-cell activation are not yet elucidated. Lipid rafts have been shown to play an important role in the compartmentalization and modulation of cell signaling. We investigated the role of DHA in modulating the lipid composition in lipid rafts and membrane subdomain distribution of interleukin-2 (IL-2) receptor signaling molecules. We found that DHA altered lipid components of rafts and modified the IL-2-induced Janus kinase-signal transducer and activator of transcription (STAT) signaling pathway by partially displacing IL-2 receptors from lipid rafts. We fractionated plasma membrane subcellular compartments and discovered that certain amounts of STAT5a and STAT5b existed in detergent-resistant plasma membrane fractions of T-cells. After DHA treatment, STAT5a and STAT5b were not detected in lipid raft fractions and were located in detergent-soluble fractions. These data demonstrate for the first time that DHA alters the lipid composition of membrane microdomains and suppresses IL-2 receptor signaling in T-cells. Thus, our data provide evidence for a functional modification in lipid rafts by DHA treatment and explain PUFA-mediated immunosuppressive effects.

Cell Membrane↗
PubMed2005

Determination of urinary nucleosides by direct injection and coupled-column high-performance liquid chromatography.

A coupled-column liquid chromatographic method for the direct analysis of 14 urinary nucleosides is described. Efficient on-line clean-up and concentration of 14 nucleosides from urine samples were obtained by using a boronic acid-substituted silica column (40 mm x 4.0 mm I.D.) as the first column (Col-1) and a Hypersil ODS2 column (250 mm x 4.6 mm I.D.) as the second column (Col-2). The mobile phases applied consisted of 0.25 mol/L ammonium acetate (pH 8.5) on Col-1, and of 25 mmol/L potassium dihydrogen phosphate (pH 4.5) on Col-2, respectively. Determination of urinary nucleosides was performed on Col-2 column by using a linear gradient elution comprising 25 mmol/L potassium dihydrogen phosphate (pH 4.5) and methanol-water (60:40, v/v) with UV detection at 260 nm. Urinary nucleosides analysis can be carried out by this procedure in 50 min requiring only pH adjustment and the protein precipitation by centrifugation of urine samples. Calibration plots of 14 standard nucleosides showed excellent linearity (r > 0.995) and the limits of detection were at micromolar levels. Both of intra- and inter-day precisions of the method were better than 6.6% for direct determination of 14 nucleosides. The validated method was applied to quantify 14 nucleosides in 20 normal urines to establish reference ranges.

Adult↗
PubMed2005

Determination of urinary 8-hydroxy-2'-deoxyguanosine by two approaches-capillary electrophoresis and GC/MS: an assay for in vivo oxidative DNA damage in cancer patients.

8-Hydroxy-2'-deoxyguanosine (8OHdG) has been considered as an excellent marker of oxidative DNA damage associated with age-related diseases such as cancer. In this paper, two sensitive methods-capillary electrophoresis with electrochemical detection (CE-ECD) and gas chromatography/mass spectrometry (GC/MS) were developed for urinary 8OHdG analysis. The R.S.D. of the spiked recovery of the two methods for determining urinary 8OHdG was 4.03% and 8.25%, respectively, and the results from the two methods have a good consistency (r=0.999, P<0.01). The developed CE-ECD method was applied to investigate the urinary 8OHdG levels in different cancer patients and follow up the response of therapy. It was found that the excretion levels of urinary 8OHdG in cancer patients were significantly higher than those in healthy persons (35.26+/-27.96 nM versus 13.51+/-5.08 nM, P<0.05), and cancer patients receiving surgical therapy and chemotherapy showed a significant decrease in urinary 8OHdG.

8-Hydroxy-2'-Deoxyguanosine↗
PubMed2005

Application of capillary zone electrophoresis in the separation and determination of the curcuminoids in urine.

The major components of the plant curcuma longa are the curcuminoids that include curcumin, demethoxycurcumin and bisdemethoxycurcumin. It has been reported the curcuminoids have some important activities. A new CZE method with diode array detection has been developed for the separation and determination of the curcumin, demethoxycurcumin and bisdemethoxycurcumin. Three curcuminoids could be readily separated within 7 min with a 15 mM sodium tetraborate buffer containing 10% methanol (v/v) at pH 10.8, 25 kV and 30 degrees C. The method has been validated and shows good performance with respect to selectivity, reproducibility, linearity, limits of detection and recovery. The proposed method was successfully applied to determine the curcuminoids in urine.

Buffers↗
PubMed2005

Rapid identification of pathogenic bacteria by capillary electrophoretic analysis of rRNA genes.

Molecular diagnosis is playing an increasingly important role in the rapid detection and identification of pathogenic organisms in clinical samples. The genetic variation of ribosomal genes in bacteria offers an alternative to culturing for the detection and identification of these organisms. Here 16S rRNA and 16S-23S rRNA spacer region genes were chosen as the amplified targets for single-strand conformation polymorphism (SSCP) and restriction fragment length polymorphism (RFLP) capillary electrophoresis analysis and bacterial identification. The multiple fluorescence based SSCP method for the 16S rRNA gene and the RFLP method for the 16S-23S rRNA spacer region gene were developed and applied to the identification of pathogenic bacteria in clinical samples, in which home-made short-chained linear polyacrylamide (LPA) was used as a sieving matrix; a higher sieving capability and shorter analysis time were achieved than with a commercial sieving matrix because of the simplified template preparation procedure. A set of 270 pathogenic bacteria representing 34 species in 14 genera were analyzed, and a total of 34 unique SSCP patterns representing 34 different pathogenic bacterial species were determined. Based on the use of machine code to represent peak patterns developed in this paper, the identification of bacterial species becomes much easier.

Bacteria↗
PubMed2005

Identification of phospholipid structures in human blood by direct-injection quadrupole-linear ion-trap mass spectrometry.

Direct-injection electrospray ionization mass spectrometry in combination with information-dependent data acquisition (IDA), using a triple-quadrupole/linear ion trap combination, allows high-throughput qualitative analysis of complex phospholipid species from child whole blood. In the IDA experiments, scans to detect specific head groups (precursor ion or neutral loss scans) were used as survey scans to detect phospholipid classes. An enhanced resolution scan was then used to confirm the mass assignments, and the enhanced product ion scan was implemented as a dependent scan to determine the composition of each phospholipid class. These survey and dependent scans were performed sequentially and repeated for the entire duration of analysis, thus providing the maximum information from a single injection. In this way, 50 different phospholipids belonging to the phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol, phosphatidylcholine and sphingomyelin classes were identified in child whole blood.

Child↗
PubMed2005

[Determination of dopamine and norepinephrine in Portulaca oleracea L. by micellar electrokinetic capillary chromatography with amperometric detection].

A method based on micellar electrokinetic capillary chromatography with electrochemical detection (MEKC-EC) was developed for the simultaneous determination of norepinephrine (NE) and dopamine (DA) in Chinese herbal plant extracts of Portulaca oleracea L. The effects of several factors such as the acidity and concentration of running buffer, sodium dodecylsulfate (SDS) concentration and detection potential were investigated to acquire the optimum conditions. The two analytes could be well separated within 12 min in a 64 cm capillary at the separation voltage of 25 kV in a 10 mmol/L phosphate buffer (pH 6.23) containing 10 mmol/L SDS. The excellent linearity was obtained in the concentration range from 1.0 x 10(-6) to 5.0 x 10(-4) mol/L. The detection limits of concentration were 4.2 x 10(-7) mol/L for NE and 8.7 x 10(-7) mol/L for DA and those of quantity were 0.41 fmol for NE and 1.45 fmol for DA at a signal-to-noise ratio of 3. This method was successfully used in the analysis of Portulaca oleracea L. without derivatization procedure, and real average contents of NE and DA in Portulaca oleracea L. were 0.015% and 0.20%, respectively.

Buffers↗
PubMed2005

[Multidimensional separations used in pharmaceutical and biological fields].

A review of multidimensional separations such as comprehensive two-dimensional gas chromatography (GC x GC), comprehensive two-dimensional high performance liquid chromatography (HPLC x HPLC) and their applications in pharmaceutical and biological fields is presented with 71 references. A single CO2 cryo-jet loop modulator was developed for GC x GC and it can be used to modulate compounds higher than C6 effectively. Comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC/TOF-MS) analyses of traditional Chinese medicine volatile oils such as Pogostemon cablin Benth (Cablin Patchouli), Forsythia suspensa (Thunb.) Vahl and Zedoary were reported also. As an emerging technology, multidimensional separations hold the promise and play an important role in the future pharmaceutical and biological fields.

Animals↗
PubMed2005

[Dead time determination of the second dimension in a comprehensive two-dimensional gas chromatography].

Comprehensive two-dimensional gas chromatography (GC x GC) is rapidly gaining importance for the analysis of complex samples. In order to predict chromatogram and optimize the operational conditions, the dead time of each dimension should be obtained exactly. Two methods to calculate the dead time of the second dimension were introduced. In the first method, based on the relationship between the time differences of a series of n-alkanes substances and the apparent retention times under different pressures, the true retention time can be calculated for non-synchronous GC x GC. The retention times of homologous series were used to calculate the dead time. Another rapid method to calculate the dead time of the second dimension is based on three or more apparent retention times in a single temperature programmed chromatographic run. The results show that the dead time of the second dimension can be calculated successfully by using the proposed methods and the deviation between the two methods is less than 0.05 s.

Algorithms↗
PubMed2005

[Development of high performance liquid chromatographic method using monolithic column for the determination of urinary nucleosides].

Modified nucleosides excreted in urine have been studied as possible bio-markers for malignant tumors. Reversed-phase high performance liquid chromatography (RP-HPLC) is one of the most popular analytical tools. However, its analysis time is longer than desired. The analytical method for urinary nucleosides has been developed using a monolithic column and a linear gradient elution of 25 mmol/L KH2PO4 solution (pH 4.55) and 60% methanol in water with UV detection at 260 nm. Twelve urinary nucleosides were completely separated. The monolithic column presented similar analytical characteristics to reversed-phase column. The time of the analysis is only 23 min, in general much shorter than the methods using a packed RP-HPLC. The method developed is sensitive, reliable and suitable for clinical applications.

Chromatography, High Pressure Liquid↗
PubMed2005

[Applications and progresses of expert system on chromatography].

The expert system on chromatography has achieved great advancement in the past two decades, and is playing a more and more important role in solving analytical problems of complex samples. Research results of expert system on chromatography in authors' group are reviewed with 64 references. A brief introduction of the expert system on chromatography is presented. Applications of the expert system on chromatography are summarized in the fields of petrochemical online analysis, environmental air sample analysis, tumor diagnosis and traditional Chinese medicine analysis. The review followed the scientific foot steps in the authors' group, starting from the development of the expert system on gas chromatography, to the selection of multi-column systems in online industrial gas chromatographs in petrochemical plants, and to the employment of the new techniques in gas chromatography, liquid chromatography and capillary electrophoresis to solve the practical analytical problems in the nation's scientific and economic development.

Chromatography↗