Biomedical subjects

Xin-Xiang Zhang

Publications and source records attributed to Xin-Xiang Zhang.

10 recordsLinked to original sources

PubMed2006

Capillary electrochromatography of amino acids with a protein-bonded porous-layer open-tubular column.

A protein-bonded porous-layer open-tubular (PLOT) column has been synthesized and applied to the separation of amino acids by CEC. The porous layer was coated on the capillary inner wall by in situ polymerization of 2-hydroxyethyl methacrylate and 2-vinyl-4,4-dimethylazlactone in the presence of 1-decanol as a porogen inside a fused-silica capillary silanized with gamma-methacryloxypropryltrimethoxysilane. The azlactone functionalities at the surface of the porous polymeric support layer were allowed to react with BSA to yield a protein-bonded PLOT column. This porous layer was characterized by scanning electron microscopy and its thickness was about 1 microm. CEC on this column gave enhanced resolution of three amino acids (histidine, phenylalanine, and tryptophan), and baseline separation was achieved with 20 mM phosphate buffer, pH 8.0.

Amino Acids↗

PubMed2006

Interaction between fluoroquinolones and bovine serum albumin studied by affinity capillary electrophoresis.

The interactions between eight fluoroquinolone antibiotics (ciprofloxacin, enoxacin, fleroxacin, levofloxacin, lomefloxacin, norfloxacin, ofloxacin, pefloxacin) and bovine serum albumin (BSA) were studied by affinity capillary electrophoresis (ACE). The binding constants were estimated by the change of migration times of the analytes through the change of concentration of BSA in the buffer solution. The yield binding constants were between 3.19 x 10(4) and 1.21 x 10(5) M(-1). These were related with the structures of fluoroquinolones, and agreed with the results obtained by other techniques. The obtained binding constants may help us in gaining some insights on possible drug/protein interactions and in early evaluation of the drugs' pharmacokinetic profiles during drug discovery.

Animals↗

PubMed2005

The interaction between severe acute respiratory syndrome coronavirus 3C-like proteinase and a dimeric inhibitor by capillary electrophoresis.

3C-like proteinase of severe acute respiratory syndrome (SARS) coronavirus has been demonstrated to be a key target for drug design against SARS. The interaction between SARS coronavirus 3C-like (3CL) proteinase and an octapeptide interface inhibitor was studied by affinity capillary electrophoresis (ACE). The binding constants were estimated by the change of migration time of the analytes in the buffer solution containing different concentrations of SARS 3CL proteinase. The results showed that SARS 3CL proteinase was able to complex with the octapeptide competitively, with binding constants of 2.44 x 10(4) M(-1) at 20 degrees C and 2.11 x 10(4)M(-1) at 37 degrees C. In addition, the thermodynamic parameters deduced reveal that hydrophobic interaction might play major roles, along with electrostatic force, in the binding process. The ACE method used here could be developed to be an effective and simple way of applying large-scale drug screening and evaluation.

3C Viral Proteases↗

PubMed2005

Study on the interaction in single antigen-antibody molecules by AFM.

The interaction between single synthesized antigen and its monoclonal antibody was directly monitored by Atomic Force Microscopy (AFM) with antigen-labeled AFM tip. The details about tip modification and antibody immobilization were described. The interactions were monitored by the change of adhesive force in separating the bound antigen-antibody. The results showed that two processes could be observed in the combination of antigen-antibody system. Possible mechanisms of rupture process as independent unbinding and cooperative unbinding were discussed. At slow separation process, the antigen-antibody linkage appeared to rupture sequentially. Increasing the separation rate from 50 nm/s to 2000 nm/s led to an increase in the possibility of cooperative unbinding. The pH influenced the affinity constants greatly, but had little effect on the magnitude of unbinding forces. The obtained results were compared with affinity constants between complete antigen and antibody obtained by immunoassay method (ELISA). The observed single rupture force between individual antibody and antigen molecules provided pertinent information relating to the manner how the antibody molecule binds to its specific antigen.

Antibodies, Monoclonal↗

PubMed2005

Development and application of a multi-target immunoaffinity column for the selective extraction of natural estrogens from pregnant women's urine samples by capillary electrophoresis.

In this paper, a methodology for the determination of three naturally occurring estrogens (estradiol, estrone and estriol) in pregnant women's urine has been described. The procedure included immunoaffinity column (IAC) extraction of 4 mL of urine sample and subsequent analysis of the extraction by micellar electrokinetic chromatography (MEKC). A multi-target polyclonal antibody that has high affinity to three estrogens was produced. Then the IAC was developed by coupling polyclonal antibody to CNBr-activated Sepharose 4B. The IAC showed high affinity for these estrogens. Recoveries of three estrogens from human serum matrix were greater than 92% with R.S.D. less than 4.5%. The final elute of urine sample was diluted with running buffer and then quantitated with MEKC. The experimental results demonstrated that IAC was a useful technique for extraction and concentration of estrogens from biological samples. Three estrogens levels in six pregnant women's urine were measured by both the present method and enzyme-linked immunoadsorbent assay (ELISA). The results of this method have been found to correlate well with those of ELISA.

Chromatography, Affinity↗

PubMed2005

Study on the interactions between anti-HIV-1 active compounds with trans-activation response RNA by affinity capillary electrophoresis.

The study on the interactions between two anti-human immunodeficiency virus type 1 (anti-HIV-1) active compounds with trans-activation response (TAR) RNA by affinity capillary electrophoresis (ACE) with UV absorbance detection is presented. The results showed that the novel active molecules could interact with TAR RNA and inhibit the reproduce process of HIV-1. The binding constants were estimated by the change of migration time of the analytes through the change of concentrations of TAR RNA in the buffer solution. The yielded binding constants of 8.87 x 10(3)M(-1) for active compound C(3) and 8.42 x 10(3)M(-1) for MC(3) at 20.0 degrees C, 0.626 x 10(3)M(-1) and 0.644 x 10(3)M(-1) at 37.0 degrees C, respectively. The thermodynamic parameters Delta H and DeltaS were obtained and shown that both hydrophobic and electrostatic interaction played roles in the binding processes. The results showed that the presented method was an easy and simple method to evaluate the interaction of small molecules with some bioactive materials.

Anti-HIV Agents↗

PubMed2004

Determination of morphine by capillary zone electrophoresis immunoassay combined with laser-induced fluorescence detection.

A competitive immunoassay for detecting morphine in bio-samples was established by capillary zone electrophoresis combined with laser-induced fluorescence detection (CZE-LIF). The antigen of morphine was labeled with isothiocyano-fluorescein (FITC) and then incubated with morphine monoclonal antibody and samples. The linear range was 50-1000 ng/mL, which was suitable for clinical and forensic applications. The detection limit can reach 40 ng/mL, based on S/N = 2. The recoveries of morphine from serum were satisfactory.

Antibody Specificity↗

PubMed2004

[Determination of the binding constants of four anti-HIV-1 active compounds with bovine serum albumin by capillary zone electrophoresis].

The binding constants (Kb) of four novel anti-HIV-1 active compounds with bovine serum albumin (BSA) were determined by capillary zone electrophoresis (CZE) with UV detection under condition of phosphate buffer (pH 8.0, 50 mmol/L) at 15 kV running voltage. These molecules were synthesized by computer-simulated design with the property of inhibiting the binding of HIV-1 Tat protein to trans-activation response region (TAR) RNA required for HIV-1 transcription and blocking the HIV replication cycle. The results showed that with the addition of different concentrations of BSA into the buffer solution, the binding constants of four active compounds (IG3, iso-C3, C3, MC3) with BSA could be measured by the change of migration time. The experimental values of Kb were 1.07 x 10(4), 1.34 x 10(4), 8.51 x 10(3) and 9.45 x 10(3) L/mol, respectively. It is an easy and simple method to estimate the interaction of small molecules with biomacromolecules with 1:1 molar binding ratio.

Animals↗

PubMed2003

Direct immunoassay of estrone by capillary electrophoresis with laser-induced fluorescence detection.

An immunoassay for estrone (E(1)) in women's serum, based on the competitive reaction between fluorescein-labeled complete antigen and E(1) with limited amount of anti-estrone monoclonal antibody is described. A thermally reversible hydrogel, poly-N-isopropylacrylamide (pNIPA), was added to the buffer to improve the reproducibility. With a laser-induced fluorescence (LIF) detector, the capillary electrophoretic immunoassay (CEIA) can be applied to determine E(1) at a concentration lower than 19.6 pg/mL. The E(1) levels in ten normal women's serum were measured at the range of 118.6-222.0 pg/mL.

Acrylic Resins↗

PubMed2002

Flow injection determination of gaseous sulfur dioxide with gas permeation denuder-based online sampling and preconcentration.

A simple and novel flow injection method for the determination of gaseous SO(2) is described based on gas permeation denuder (GPD) online sampling and preconcentration. The GPD is easily prepared with poly(vinylidene) difluoride microporous membrane as gas permeable material and two Perspex blocks with smooth and flat interface and rectangular engraved channels of mirror image. The sample gas is on one side of the membrane and phosphate buffer of pH 7.0 as the absorbing solution is on the other side. Gaseous SO(2) permeates partially through the gas permeable membrane and dissolves in the absorbing solution. After preconcentration for 5.0 or 8.0 min, the solution is injected into the flow of 5.0 x 10(-4) mol L(-1) 5,5'-dithiobis(2,2'-dinitrobenzoic acid) (DTNB) in 0.025 mol L(-1) phosphate buffer. The resulting product formed between DTNB and absorbed SO(2) is spectrophotometrically monitored at 410 nm with a charge coupled device (CCD) fiber optic spectrometer. The calibration graphs for preconcentration of 5.0 and 8.0 min are linear up to 4.0 and 3.2 mg m(-3) with detection limits of 50 and 35 micro g m(-3), respectively. The corresponding analysis speeds are 8.5 and 6 samples h(-1). The method is selective and just suffer from interference of hydrogen sulfide at higher than 1% of SO(2) level (in m/V) with an error >+10%. The assay just uses cheap and common membrane and reagents and shows potential application in the monitoring of atmospheric SO(2).

Journal Article↗