Biomedical subjects

Qin Wei

Publications and source records attributed to Qin Wei.

30 records · Page 2Linked to original sources

PubMed2004

Plant regeneration from epicotyl explant of Jatropha curcas.

In vitro epicotyl explants from Jatropha curcas were cultured on MS medium with indole-3-butyric acid (IBA) and 6-benzyladenine (BA). Adventitious buds were directly induced from the surface of epicotyl explants under the condition with the combinations of IBA 0.1 mg/L and BA 0.2-0.7 mg/L. Of which IBA 0.1 mg/L and BA 0.5 mg/L induced the highest regeneration frequency. Shoot regeneration from callus required the combinations of IBA 0.5 mg/L with BA 0.1 mg/L, IBA 0.5 mg/L with BA 0.2 mg/L and IBA 1.0 mg/L with BA 0.5 mg/L, and the most suitable combination was IBA 1.0 mg/L and BA 0.5 mg/L. The health adventitious buds and regenerated shoots could be rooted on growth regulator-free MS medium. Regenerated plants with well developed shoots and roots were successfully transferred to greenhouse, without visible detectable variation.

Adenine↗

PubMed2004

[Spectrophotometric determination of trace amount of lead with trimethoxyphenylfluorone in microemulsion after using sulphydryl dextran gel for preconcentration and separation].

In this paper, the color reaction of lead with trimethoxyphenylfluorone (TM-PF) in microemulsion has been studied. Lead (II) reacts with TM-PF to form a stable 1:2 complex at pH 9.1. Its apparent molar absorptivity is 5.32 x 10(4) L x mol(-1) x cm(-1) at 565 nm. Beer's law is obeyed in the range of 0-1.5 microg x mL(-1). Sulphydryl dextran gel (SDG), in which sulphydryl group has a big share, is a new type of metallic ion adsorbent. It presents the advantage of higher adsorption capacity, better reuse ability and higher mechanical stability. So the coexistent metal ions can be separated effectively and lead can be enriched by SDG, greatly improving the selectivity and sensibility of the system. The method was used to determine trace amount of lead in blood, hair and urine samples with satisfactory results.

Chromatography, Gel↗

PubMed2003

Analysis of the 3(')-hydroxyl group in Drosophila siRNA function.

Members of the RNA-dependent RNA polymerase (RdRP) gene family have been shown to be essential for dsRNA-mediated gene silencing based on genetic screens in a variety of organisms, including Caenorhabditis elegans, Arabidopsis, Neurospora, and Dictyostelium. A hallmark of this process is the formation of small 21- to 25-bp dsRNAs, termed siRNAs for small interfering RNAs, which are derived from the dsRNA that initiates gene silencing. We have developed methods to demonstrate that these siRNAs produced in Drosophila embryo extract can be uniformly incorporated into dsRNA in a template-specific manner that is subsequently degraded by RNase III-related enzyme activity to create a second generation of siRNAs. SiRNA function in dsRNA synthesis and mRNA degradation depends upon the integrity of the 3'-hydroxyl of the siRNA, consistent with the interpretation that siRNAs serve as primers for RdRP activity in the formation of dsRNA. This process of siRNA incorporation into dsRNA followed by degradation and the formation of new siRNAs has been termed "degradative PCR" and the proposed mechanism is consistent with the genetic and biochemical data derived from studies in C. elegans, Arabidopsis, Drosophila, and Dictyostelium. The methods used to study the function of both natural and synthetic siRNAs in RNA interference in Drosophila embryo extracts are detailed. The importance of the 3'-hydroxyl group for siRNA function and its incorporation into dsRNA is emphasized and the results support a model that places RNA-dependent RNA polymerase as a key mediator in the RNA interference mechanism in Drosophila.

Animals↗

PubMed2003

Purification, characterization and biological activity of an L-amino acid oxidase from Trimeresurus mucrosquamatus venom.

An L-amino acid oxidase (TM-LAO) from the venom of Hunan Trimeresurus mucrosquamatus was purified to homogeneity by three steps including DEAE Sephadex A-50 ion-exchange chromatography, Sephadex G-75 gel filtration and Resource Q ion-exchange chromatography. TM-LAO is composed of two identical subunits with a molecular weight of 55 kD by SDS-polyacrylamide gel electrophoresis. The molecular weight was different with that of LAO purified from the same species distributed in Taiwan that was 70 kD. The 24 N-terminal amino acid sequence of TM-LAO is ADNKNPLEECFRETNYEEFLEIAR, which shares high similarity with other Viperid snake venom LAOs and has moderate similarity with Elapid snake venom LAOs. Further studies found that TM-LAO inhibited the growth of E. coli, S. aurues and B. dysenteriae. TM-LAO also showed cytotoxicity and platelet aggregation activity. All the biological activities were eliminated by catalase, a H(2)O(2) scavenger. It was shown that these biological effects were possibly due to the formation of H(2)O(2) produced by TM-LAO.

Amino Acid Oxidoreductases↗

PubMed2002

Purification and cloning of a novel C-type lectin-like protein with platelet aggregation activity from Trimeresurus mucrosquamatus venom.

TMVA, a novel C-type lectin-like protein that induces platelet aggregation in a dose-dependent manner, was purified from the venom of Trimeresurus mucrosquamatus. It consists of two subunits, alpha (15536 Da) and beta (14873 Da). The mature amino acid sequences of the alpha (135 amino acids) and beta subunits (123 amino acids) were deduced from cloned cDNAs. Both of the sequences show great similarity to C-type lectin-like venom proteins, including a carbohydrate recognition domain. The cysteine residues of TMVA are conserved at positions corresponding to those of flavocetin-A and convulxin, including the additional Cys135 in the alpha subunit and Cys3 in the beta subunit. SDS-PAGE, mass spectrometry analysis and amino acid sequence showed that native TMVA exists as two convertible multimers of (alpha beta)(2) and (alpha beta)(4) with molecular weights of 63680 and 128518 Da, respectively. The (alpha beta)(2) complex is stabilized by an interchain disulfide bridge between the two alpha beta-heterodimers, whereas the stabilization of the (alpha beta)(4) complex seems to involve non-covalent interactions between the (alpha beta)(2) complexes.

Amino Acid Sequence↗

PubMed2002

Purification and characterization of alpha-mucrofibrase, a novel serine protease with alpha-fibrinogenase activity from the venom of Chinese Habu (Trimeresurus mucrosquamatus).

A novel fibrinogenolytic protease, named alpha-mucrofibrase, was purified from the venom of Chinese Habu (Trimeresurus mucrosquamatus) by DEAE-Sephadex A-50 ion-exchange chromatography and Sephadex G-100 (super fine) gel filtration alpha-Mucrofibrase is a single-chain polypeptide of approximately 29 kDa. It is stable even at 95 degrees C, and the most susceptible hydrolysis substrate is S-2302. It cleaved primarily the Aalpha chain of fibrinogen followed by the Bbeta chain, while the gamma chain was partially affected. N-terminal sequence of this fibrinogenolytic enzyme has great homology with those of other snake venom serine proteases. The esterase activity of alpha-mucrofibrase is inhibited by phenylmethylsulfonyl fluoride (PMSF) but not by metal chelator (EDTA), suggesting this fibrinogenase belongs to the venom serine protease family.

Amino Acid Sequence↗

PubMed2002

L-amino acid oxidase from Trimeresurus jerdonii snake venom: purification, characterization, platelet aggregation-inducing and antibacterial effects.

An L-amino acid oxidase (LAO), designated as TJ-LAO, was purified to homogeneity from the venom of Trimeresurus jerdonii by Sephadex G-100 and Q Sepharose HP chromatography. The molecular weight of this enzyme was 110 kD as estimated by analytical gel filtration and was 55 kD by SDS-polyacrylamide gel electrophoresis, suggesting that the enzyme is composed of two subunits. The enzyme has an absorption spectrum characteristic of flavoproteins, containing 2 moles of FMN per mole of enzyme. The N-terminal sequence of TJ-LAO shares high homology with other viperid snake venom LAOs. Homology with elapid venom LAO is lower. TJ-LAO inhibited the growth of Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus megaterium. The antibacterial effect associated with LAO activity was elminated with the addition of catalase. Platelets in platelet-rich plasma aggregated upon the addition of TJ-LAO. The enzyme-induced aggregation was inhibited by catalase, suggesting formation of H2O2 was essential for TJ-LAO to induce platelet aggregation. These results showed H2O2 formation is important for the biological effects of LAO.

Amino Acid Oxidoreductases↗

PubMed2002

[Determination of trace iron by catalytic spectrophotometry with nile blue].

A new method is developed for the determination of trace iron, which is used to catalyze the discoloring reaction of KBrO3 oxidizing nile blue in acid medium in the presence of NTA. The kinetics is studied. The method has high sensitivity and the range of determination is 0-0.4 microgram/25 mL for iron. The detection limit of the method is 4.73 x 10(-10) g/mL. Satisfactory results are obtained for the determination of trace iron in food and water.

Catalysis↗

PubMedDate not supplied

High sensitive fluorophotometric determination of nucleic acids with Pyronine G sensitized by N,N-dimethylformamide.

In Tris-HCl buffer (pH 8.0), the fluorescence of Pyronine G emitted at 552 nm was quenched by nucleic acids when excited at 525 nm. Adding N, N-dimethylformamide (DMF) as a sensitive media can enhance the sensitivity greatly. Based on the fluorescence reactions sensitive fluorimetric methods for nucleic acids at nanogram levels were proposed. Under the optimum conditions, the calibration curves were linear in the range of 0.0032 - 2.5 microg mL(-1) for ct DNA and 0.0024 - 2.5 microg mL(-1) for hs DNA. The limits of determination were 3.2 ng mL(-1) and 2.4 ng mL(-1) respectively. This method has good selectivity and high sensitivity. It has been applied to the determination of DNA in the synthetic samples and real samples with satisfactory results.

Animals↗

PubMedDate not supplied

Studies and application of catalytic kinetic spectrophotometric determination of trace chromium(VI) sensitized by microemulsion medium.

A new catalytic kinetic spectrophotometric method for the determination of trace amount of chromium (VI) in microemulsion medium has been developed. The method is based on the catalytic effect of chromium (VI) on the oxidation of nuclear fast red in the presence of Tween-80 microemulsion and HAc-NaAc buffer solution (pH = 5.2). The linear ranges are in the range of 0 approximately 0.0480 microg mL(-1) of Cr (VI) at 528 nm and the detection limit is 1.56x10(-9)g mL(-1). The method has been applied in determination of Cr (VI) in water and food samples with satisfactory results. The relative standard deviation is less than 4.6 % and the recovery is 93.5 approximately 104 %.

Acetic Acid↗

PubMedDate not supplied

Determination of protein in milk powder using 2-sulfophenylazo-rhodanine as a probe by the enhanced resonance Rayleigh light-scattering technique.

In this paper, the interaction between 2-sulfophenylazo-rhodanine and protein was investigated by Rayleigh light-scattering technique. Based on this, a novel method for the determination of protein was developed. The effects of different conditions, such as acidity and media, were investigated thoroughly, and the optimum conditions were confirmed. Bis(2-ethylhexyl)sulfosuccinate (AOT) microemulsion, which is introduced into the protein determination, markedly increased the sensitivity of the system by changing the microenvironment. In pH 2.80 Britton-Robinson buffer solution in the presence of AOT microemulsion, the detection limits of bovine serum albumin, human serum albumin, ovalbumin, and gamma-globulin are 5.4, 4.5, 9.8, and 10.1 ng/mL, respectively. The method developed in this paper has been applied to the determination of protein in milk powder with satisfactory results.

Animals↗

PubMedDate not supplied

Determination of nucleic acids using fluorescence probe sensitized by microemulsion.

Because the fluorescence of azur A can be quenched by adding nucleic acid, a sensitive fluorometric method for determination of nucleic acids at nanogram levels was established. Using optimal conditions, the calibration curves were linear in the range of 0-6.0 microg/mL for calf thymus deoxyribonucleic acid (ct DNA) and 0-7.0 microg/mL for herring sperm DNA (hs DNA). The limits of determination were 3.5 and 3.8 ng/mL, respectively, which shows the high sensitivity of this method. Triton X-100 microemulsion was applied as a sensitive media to enhance the sensitivity. The binding mode concerning the interactions of azur A with nucleic acids was also studied and the association constant with different binding numbers was obtained. The method has been applied to the determination of nucleic acid in both synthetic and real samples, such as cauliflower and pork liver, with satisfactory results.

Algorithms↗