Biomedical subjects

Feng Tan

Publications and source records attributed to Feng Tan.

17 recordsLinked to original sources

PubMed2006

[Preparation, characterization and preliminary application of recombinant protein AP33 of trichomonas vaginalis].

OBJECTIVE: To clone ap33 gene of Trichomonas vaginalis( T. v), construct prokaryotic expression system of the gene and identify its antigenicity and immunogenicity. METHODS: The total RNA was extracted from a clinical isolate Tv317 and the cDNA was synthesized by reverse transcription. The ap33 gene from cDNA of Tv317 was amplified by PCR. The nucleotide sequence of the target DNA amplification fragment was sequenced after T-A cloning. The expression vector pET32a (+) with inserted ap33 gene was constructed. Recombinant fusion protein AP33 was expressed in E. coli strain BL21DE3 induced by IPTG at different dosages. Western blotting was applied to determine immunoreactivity of the recombinant fusion protein AP33 with antibody against whole cell of T. v. Double agar diffusion was applied to determine immunogenicity of the recombinant fusion protein AP33 with rabbit antiserum immunized with the recombinant fusion protein AP33, and ELISA with antigen of T. v whole cell was applied to determine immunogenicity of the recombinant protein AP33. Positive human sera were tested by ELISA with the recombinant fusion protein AP33. RESULTS: High homology of nucleotide and amino acid sequences was revealed between the cloned ap33 and the corresponding gene. The recombinant protein showed a high expression level. The recombinant protein was recognized by anti-T. v polyclonal antibody from rabbit, and showed a high titer. The clinical T. v isolates showed high ap33 expression level and stimulated the production of specific antibody. Antibody against AP33 was detected in 78% of the 50 patients infected with T. v by ELISA. CONCLUSION: A prokaryotic expression system of T. v ap33 gene has been established. The expressed fusion protein AP33 shows satisfactory antigenicity and immunogenicity.

Animals↗

PubMed2006

Study of conical columns with 10 degrees opening angle for preparative liquid chromatography.

The efficiency and sample capacity of conical liquid chromatographic columns with 10 degrees opening angle were studied at different ratio of cross section areas of inlet to outlet (A(in)/A(out)) and column dimension. As the A(in)/A(out) ratio changed from 4 to 2.25, the reduced plate height (h) was reduced and the h value decreased 12% when the column dimension was scaled up proportionally because of relatively smaller dead volume on both end of the column. Compared to cylindrical columns having corresponding lengths and volumes, the conical columns with 10 degrees opening angle were superior in column efficiency, resolution and the maximum peak concentration at column outlet; the loadability of conical column was improved 30-40% on injection volume and 50-60% on sample mass, respectively, over cylindrical columns.

Chromatography, Liquid↗

PubMed2005

[Detection of Angiostrongylus cantonensis circulating antigen by monoclonal antibodies].

OBJECTIVE: To prepare monoclonal antibodies (McAbs) against soluble antigens of adult worms of Angiostrongylus cantonensis (A. cantonensis) on the purpose to detect CAg of A. cantonensis. METHODS: Female BALB/c mice were immunized with soluble antigens of adult worms of A. cantonensis and the spleen cells were fused with myeloma SP2/0 cells. The hybridoma cell strains were screened by enzyme-linked immunosorbent assay (ELISA) and Western blotting. Two McAbs (3F1 and 4H2) were applied to detect the CAg in the sera of rats and mice infected with A. cantonensis and angiostrongyliasis patients respectively by double antibody sandwich ELISA. RESULTS: Three McAbs against A. cantonensis adult were obtained. Two McAbs (3F1, 4H2) were identified as IgG1 and one McAb (2A2) was identified as IgM. The titers of culture fluid and ascites was 1:25,600, 1:25,600, 1:12,800 and 1:80,000, 1:80,000, 1:40,000 respectively. Western blotting results showed three McAb could be used to identify 15,000 protein of adult worms of A. cantonensis. The detection rates of the CAg in the sera of infected rats and mice were 84.2% (48/57) and 87.2% (41/47) respectively. The detection rate of the CAg in the sera of angiostrongyliasis patients was 86.4% (19/22), and no cross reactions with sera from patients with schistosomiasis, cysticercosis cellulose, paragonimiasis and trichinellosis were observed. The CAg in the sera from mice examined at different periods after infection revealed positive 2 week after inoculation and the titer of CAg peaked 4 week after inoculation. CONCLUSION: A new method of sandwich ELISA with high sensitivity and specificity to detect the serum A. cantonensis CAg has been obtained, it could be applicable to the diagnosis, observation of curative effect and epidemiology of angiostrongyliasis.

Angiostrongylus cantonensis↗

PubMed2005

[Preparation and preliminary application of monoclonal antibodies against adult worm of Angiostrongylus cantonensis].

OBJECTIVE: To develop and identify monoclonal antibodies (McAbs) against adult worm of Angiostrongylus cantonensis and observe its applicability. METHODS: BALB/c mice were immunized with soluble antigen of adult worms of A. cantonensis. The spleen cells of immunized mice were fused with myeloma cell, and the hybridoma secreting high titer of McAbs with high specificity was screened. By using the McAbs, serum of angiostrongyliasis patient and sera of the rats infected with A. cantonensis were detected by Western blotting and double antibody sandwich ELISA respectively. RESULTS: Three McAbs were established (2A2, 3F1, 4H2), which all showed no cross reaction with antigens of Schistosoma japonicum, Paragonimus westermani, Cysticercus cellulosae and Trichinella spiralis. Western blotting analysis demonstrated that the three McAbs recognized a Mr 15,000 soluble antigen of adult worm of A. cantonensis and recognized the Mr 24,000 and Mr 15,000 circulating antigens from the serum of angiostrongyliasis patient. The double antibody sandwich ELISA detection showed a positive rate of 76.5%. CONCLUSION: Three hybridoma cell lines against adult worm of A. cantonensis have been established which secret high titer of McAbs with high specificity and seem promising in detecting the circulating antigen of the angiostrongyliasis patient.

Angiostrongylus cantonensis↗

PubMed2005

Molecular cloning and characterization of a 1-deoxy-D-xylulose 5-phosphate reductoisomerase gene from Ginkgo biloba.

1-deoxy-D-xylulose 5-phosphate (DXP) reductoisomerase (DXR, EC: 1.1.1.267) is the second enzyme of the non-mevalonate terpenoid pathway for isopentenyl diphosphate biosynthesis and actually catalyzes a committed step of the methylerythritol phosphate (MEP) pathway for ginkgolide biosynthesis. The full-length DXR cDNA sequence (GenBank accession number: AY443101) was cloned and characterized for the first time from gymnosperm plant species, Ginkgo biloba, using rapid amplification of cDNA ends (RACE) technique. The full-length cDNA of GbDXR was 1720 bp containing a 1431 bp open reading frame (ORF) encoding a peptide of 477 amino acids with a calculated molecular mass of 52 kDa and an isoelectric point of 6.58. Comparative and bioinformatic analyses revealed that GbDXR showed extensive homology with DXRs from other plant species and contained a conserved transit peptide for plastids, an extended Pro-rich region and a highly conserved NADPH binding motif in its N-terminal region owned by all plant DXRs. Phylogenetic analysis indicated that GbDXR was more ancient than other plant DXRs. Tissue expression pattern analysis indicated that GbDXR expressed in all tissues including roots, stems, leaves, pericarps and seeds and lower transcription level was observed in leaves of G. biloba than that of other tissues. The cloning and characterization of GbDXR will be helpful to understand more about the role of DXR involved in the ginkgolides biosynthesis at the molecular level.

Aldose-Ketose Isomerases↗

PubMed2005

A novel microcomputer temperature-compensating method for an overtone crystal oscillator.

In this paper, a novel microcomputer temperature-compensating method for an overtone crystal oscillator (MCOXO) is presented. In this method, a ceramic oscillator is chosen, and its output frequency is mixed with the output frequency of an overtone crystal oscillator. A crystal filter is used to suppress the spurious mixing products. A microcomputer is used to control the switch capacitance array that is connected to the ceramic oscillator circuit. The frequency deviation of the crystal oscillator is directly compensated by the output frequency of the ceramic oscillator. As a result, the method is able to overcome the disadvantages of frequency stability degradation and phase noise deterioration that are provoked by adding inductance or frequency multiplication in traditional compensating approaches. At the same time, this method is able to compensate a quite wide frequency range and many types of oscillators, not just crystal oscillators. The experimental compensating results show that, using this method, the frequency-temperature stability of a 100 MHz 5th overtone temperature-compensated crystal oscillator can achieve < or = +/-2 x 10(-6) for 0-70 degrees C.

Journal Article↗

PubMed2005

Simultaneous light emitting diode-induced fluorescence and contactless conductivity detection for capillary electrophoresis.

A combined detection system of simultaneous contactless conductometric and fluorescent detection for capillary electrophoresis (CE) has been designed and evaluated. The two processes share a common detection cell. A blue light-emitting diode (LED) was used as the excitation source and an optical fiber was used to collect the emitting fluorescence for fluorescent detection (FD). Inorganic ions, fluorescein isothiocyanate (FITC)-labeled amino acids and small molecule peptides were separated and detected by the combined detector, and the detection limits (LODs) of sub-microM level were achieved.

Journal Article↗

PubMed2005

Determination of heavy metal ions by capillary electrophoresis with contactless conductivity detection after field-amplified sample injection.

A method has been developed for determining of heavy metal ions by field-amplified sample injection capillary electrophoresis with contactless conductivity detection. The effects of the 2-N-morpholinoethanesulfonic acid/histidine (MES/His) concentration in the sample matrix, the injection time and organic additives on the enrichment factor were studied. The results showed that MES/His with a low concentration in the sample matrix, an increase of the injection time and the addition of acetonitrile improved the enrichment factor. Four heavy metal ions (Zn2+, Co2+, Cu2+ and Ni2+) were dissolved in deionized water, separated in a 10 mM MES/His running buffer at pH 4.9 and detected by contactless conductivity detection. The detection sensitivity was enhanced by about three orders of magnitude with respect to the non-stacking injection mode. The limits of detection were in the range from 5 nM (Zn2+) to 30 nM (Cu2+). The method has been used to determine heavy metal ions in tap water.

Journal Article↗

PubMed2005

[Effect of erigeron injection on platelet level of CD62p and serum content of TNF-alpha and IL-6 in patients with acute cerebral infarction].

OBJECTIVE: To investigate the clinical effect of Erigeron injection (El) on positive expression rate of CD62p in platelet and content of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in serum of patients with acute cerebral infarction (ACI). METHODS: Sixty-eight patients with ACI were randomly divided into the treated group (n = 35) and the control group (n = 33). Conventional treatment were given to both groups, and EI 40 ml/d were given additionally to the treated group, the treatment course for both groups was 15 days. The positive expression of platelet CD62p and the serum TNF-alpha and IL-6 in patients before and after treatment were determined with flow cytometric (FCM) and electrochemical-luminescence (ECL) techniques respectively. RESULTS: The total curative effect in the treated group were significantly higher than that in the control group (P < 0.05). Levels of platelet CD62p and serum TNF-alpha and IL-6 in ACI patients before and after treatment were significant higher than those in the healthy group (P < 0.05), all the three parameters were significantly decreased after treatment, and the lowering in the treated group was more significant than that in the control group (P < 0.05). CONCLUSION: The effect of El on ACI patients may relate to its action in down-regulating the expression of platelet CD62p, alleviating the immune response and inflammatory injury of central nervous system induced by cytokines.

Aged↗

PubMed2005

[Capacitively coupled contactless conductivity detection in capillary electrophoresis].

Capacitively coupled contactless conductivity detection (C4D) is a new detection technique has been developed in recent years and used mainly in capillary electrophoresis and microchip electrophoresis. The characteristics of C4D detector are simple in structure, easy in miniaturization and integration, and free of electrodes contamination, which are common problems in an electrochemical detection. The principles and progresses of C4D in capillary electrophoresis are reviewed.

Conductometry↗

PubMed2005

[A novel light-emitting diode-induced fluorescence detector for micro-scale flow analysis system].

A compact light-emitting diode-induced fluorescence detector based on collinear scheme is described. The detector was assembled by all-solid-state optical-electronic components and easily coupled with micro-scale flow analysis system by on-column detection mode. Fluorescein isothiocyanate (FITC) and FITC-labeled amino acids were used as test analytes to evaluate the detector performance by capillary electrophoresis and flow injection analysis techniques. The concentration limit of detection was 10(-8) mol x L(-1) for FITC-labeled phenylalanine at a signal-to-noise ratio (S/N) of 3 (on-column, 0.05 mm i.d.). The system exhibited a good linear response in the range of 1 x 10(-7) -2 x 10(-5) mol x L(-1) (r2 = 0.999). The relative standard deviation (RSD) of 6 repetitive injections on peak heights is less than 3%.

English Abstract↗

PubMed2004

A new geranylgeranyl diphosphate synthase gene from Ginkgo biloba, which intermediates the biosynthesis of the key precursor for ginkgolides.

Geranylgeranyl diphosphate synthase (GGPPS, EC: 2.5.1.29) catalyzes the biosynthesis of geranylgeranyl diphosphate (GGPP), which is a key precursor for ginkgolide biosynthesis. Here we reported for the first time the cloning of a new full-length cDNA encoding GGPPS from the living fossil plant Ginkgo biloba. The full-length cDNA encoding G. biloba GGPPS (designated as GbGGPPS) was 1657bp long and contained a 1176bp open reading frame encoding a 391 amino acid protein. Comparative analysis showed that GbGGPPS possessed a 79 amino acid transit peptide at its N-terminal, which directed GbGGPPS to target to the plastids. Bioinformatic analysis revealed that GbGGPPS was a member of polyprenyltransferases with two highly conserved aspartate-rich motifs like other plant GGPPSs. Phylogenetic tree analysis indicated that plant GGPPSs could be classified into two groups, angiosperm and gymnosperm GGPPSs, while GbGGPPS had closer relationship with gymnosperm plant GGPPSs.

Alkyl and Aryl Transferases↗

PubMed2004

Molecular cloning and sequence analysis of a novel chalcone synthase cDNA from Ginkgo biloba.

A chalcone synthase (CHS) gene was cloned from Ginkgo biloba for the first time and it was also the first cloned gene involved in flavonoids metabolic pathway in G. biloba. The full-length cDNA of G. biloba CHS (designated as Gbchs) was 1608bp with poly(A) tailing and it contained a 1173bp open reading frame (ORF) encoding a 391 amino acid protein. Gbchs was found to have extensive homology with those of other plant chs genes via multiple alignments. The active sites of the CoA binding, coumaroyl pocket and cyclization pocket in CHS protein of Medicago sativa were also found in GbCHS. Molecular modeling of GbCHS indicated that the three-dimensional structure of GbCHS strongly resembled that of M. sativa (MsCHS2), implying GbCHS may have similar functions with MsCHS2. Phylogenetic tree analysis revealed that GbCHS had closer relationship with CHSs from gymnosperm plants than from other plants. Gbchs is a useful tool to study the regulation of flavonoids metabolism in G. biloba.

Acyltransferases↗

PubMed2004

[Design of laser-induced fluorescence detector for high performance liquid chromatography].

Based on confocal configuration, a laser-induced fluorescence detector (LIFD) for high performance liquid chromatography (HPLC) is described and evaluated. A diode double-pumped solid-state laser emitting at 473 nm is used as excitation source. A detection cell of 7 microL physical volume and 0.1 nL effective optical volume was designed for conventional HPLC-LIFD. The angle between entrance and outlet channels of the cell was 120 degrees, without any change of internal diameters or right-angles along the channels. These measures insured the elimination of bubble accumulation or formation inside the cell, and additional band broadening effect. Riboflavin standard was used as test sample to evaluate the performance of the HPLC-LIFD. The analyses of real samples containing riboflavin were demonstrated.

Chromatography, High Pressure Liquid↗

PubMed2003

Molecular cloning and characterization of a novel lectin gene from Zephyranthes candida.

A new lectin gene was cloned from Zephyranthes candida by using RACE-PCR. The full-length cDNA of Zephyranthes candida agglutinin (ZCA) was 647 bp and contained a 477 bp open reading frame encoding a 159 amino acid protein. Zephyranthes candida lectin gene was found to encode a precursor lectin with signal peptide and had extensive homology with those of other plant lectins. Molecular modeling of ZCA indicated that the three-dimensional structure of ZCA strongly resembles that of the snowdrop lectin, implying ZCA may have the similar insecticidal functions with GNA.

Amino Acid Sequence↗

PubMed2003

[Solid phase microextraction and derivatization of sulfide in blood with pentafluorobenzylbromide].

Solid phase microextraction (SPME) and derivatization with pentafluorobenzylbromide for sulfide in blood was presented in the paper. The derivative of sulfide was extracted for 20 min at the condition of room temperature by a polydimethylsiloxane fiber. 1,3,5-tribromobenzene (IS) was used as an internal standerd. GC/MS was used for analysis. The ions at m/z 394 (derivative of sulfide) and m/z 312 (IS) in the selected ion minitoring chromatograms were selected for quantitation. The compound was detectable at least 0.01 microgram/ml. By the determination in poisoning blood, this method would be demonstrated to be simple.

Benzene Derivatives↗

PubMedDate not supplied

[An intron-free methyl jasmonate inducible geranylgeranyl diphosphate synthase gene from Taxus media and its functional identification in yeast].

Geranylgeranyl diphosphate synthase (GGPPS, EC: 2.5.1.29) catalyzes the biosynthesis of geranylgeranyl diphosphate (GGPP), which is a key precursor for diterpenes including Taxol, one of the most potent antitumor drugs. In order to investigate the role of GGPP synthase in taxol biosynthesis, we cloned, characterized and functionally expressed the GGPP synthase gene from Taxus media. A 3743-bp genomic sequence of T. media was isolated by genome walking strategy which contained an 1182-bp open reading frame (ORF) encoding a 393-amino acid polypeptide that showed high similarity to other plant GGPPSs. Subsequently the full-length cDNA of the GGPPS gene of T. media (designated TmGGPPS) was amplified by RACE. Bioinformatic analysis showed that TmGGPPS was an intron-free gene and its deduced polypeptide contained all the five conserved domains and functional aspartate-rich motifs of the prenyltransferases. By constructing the phylogenetic tree of plant GGPPSs, it was found that plant-derived GGPPSs could be divided into two classes, angiosperm and gymnosperm classes, which might have evolved in parallel from the same ancestor. To our knowledge this was the first report that the geranylgeranyl diphosphate synthase genes were free of intron and evolved in parallel between angiosperms and gymnosperms. The coding sequence of TmGGPPS was expressed in yeast mutant (SFNY368) lacking of GGPP synthase activity through functional complementation, and the transgenic yeast showed to have activity of GGPP synthase. This was also the first time to use SFNY368 to identify the function of plant-derived GGPPSs. Furthermore, investigation of the impact of methyl jasmonate (MeJA) on the expression of TmGGPPS revealed that MeJA-treated T. media cultured cells had much higher expression of TmGGPPS than untreated cells.

Acetates↗