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Biomedical subjects

Feng Wang

Publications and source records attributed to Feng Wang.

243 records · Page 14Linked to original sources
PubMed2002

[Determination of trace barium in environmental samples by electric-heated AAS with lanthanum-coated graphite tube].

In this paper a new method was established for determination of trace barium in environmental samples by graphite furnace atomic absorption spectrometry. In the presence of matrix modifier magnesium nitrate, the matrix inference was eliminated efficiently. To avoid producing barium carbide, the graphite tubes were coated differently with lanthanum, zirconium, tungsten, molybdenum, and tantalum. Results showed that the tube with lanthanum was the best. The atomization temperature was diminished. The sensitivity was improved, and the tube with lanthanum gave the longest service life. So we used the tube to determine trace barium. The trace barium in Geodchemical Standard Reference Sample Soil-1 (GSS-1) was determined by the new method, the test results showed that the method was reliability and accurate. The method has been used for the determination of trace barium in environmental samples and in water of Yellow River. The detection limit for Ba was 2.1 x 10(-12) g and the relative standard deviation(RSD) was 5.4% for 15 ng.mL-1 Ba.

Barium↗
PubMed2000

Mechanism of exogenous nucleic acids and their precursors improving the repair of intestinal epithelium after gamma-irradiation in mice.

AIM:To clone expressed genes associated with repair of irradiation-damaged mice intestinal gland cells treated by small intestinal RNA, and to explore the molecular mechanism of exogenous nucleic acids improving repair of intestinal crypt.METHODS:The animal mode of test group and control group was established, forty-five mice being irradiated by gamma ray were treated with small intestinal RNA as test group, forty mice being irradiated by gamma ray were treated with physiological saline as control group,five mice without irradiation were used as normal control, their jejunal specimens were collected respectively at 6h, 12h,24h, 4d and 8d after irradiation. Then by using LD-PCR based on subtractive hybridization, these gene fragments differentially expressed between test group and control group were obtained, and then were cloned into T vectors as well as being sequenced. Obtained sequences were screened against. GeneBank, if being new sequences, they were submitted to GeneBank.RESULTS:Ninety clones were associated with repair of irradiation-damaged intestinal gland cells treated by intestinal RNA. These clones from test group of 6h, 12h, 24h, 4d and 8d were respectively 18, 22, 25, 13, 12. By screening against GeneBank, 18 of which were new sequences, the others were dramatically similar to the known sequences, mainly similar to hsp, Nmi,Dutt1, alkaline phosphatase, homeobox, anti-CEA ScFv antibody, arginine/serine kinase and BMP-4,repA. Eighteen gene fragments were new sequences,their accept numbers in GeneBank were respectively AF240164-AF240181.CONCLUSION:Ninety clones were obtained to be associated with repair of irradiation damaged mice intestinal gland cells treated by small intestinal RNA, which may be related to abnormal expression of genes and matched proteins of hsp, Nmi, Dutt1, Na, K-ATPase,alkalineph-osphatase, glkA, single stranded replicative centromeric gene as well as 18 new sequences.

Journal Article↗
PubMed1999

Synthesis of B- and P-Heterocycles by Reaction of Cyclic Acetals and Ketals with Borinium and Phosphonium Ions.

Tricoordinated cyclic boron cations result from gas-phase ion/molecule reactions of dicoordinated borinium ions with neutral acetals and ketals and thiazolidine. The reaction, which proceeds via initial cationic binding to a heteroatom followed by a consecutive ring-opening and ring-reclosing process, resembles the Eberlin transacetalization of acylium ions (Eberlin, M. N.; Cooks, R. G. Org. Mass Spectrom. 1993, 28, 679). The cyclic structure of the tricoordinated boron cation is demonstrated by tandem mass spectrometry and further confirmed by comparison with authentic cyclic tricoordinated boron cations. The five-membered cyclic boron cations dissociate by ethylene oxide loss to thus reform the reactant-dicoordinated borinium ion; the six-membered boron cations fragment instead by ethylene loss. Consistent with the proposed mechanism, the ion/molecule reaction efficiency falls in the order CH(3)OB(+)C(2)H(5) > CH(3)OB(+)OCH(3) >> CH(3)B(+)CH(3); i.e., the higher the nucleophilicity of the borinium ion, the higher the reaction efficiency. A potential energy surface is calculated for the reaction of CH(3)OB(+)OCH(3) with 2-methyl-1,3-dioxolane, and the reaction is found to be 43.3 kcal/mol exothermic due to initial formation of a strong B-O bond. The analogous reactivity displayed by phosphonium ions is also investigated by both experiment and ab initio calculations. In contrast to the borinium ions, the phosphonium ions exhibit higher regioselectivity for sulfur compared to nitrogen and oxygen. Finally, the present findings indicate that the reaction exothermicity and the regioselectivity are controlled by both the Lewis acidity of the reactant cations and the leaving ability of the released neutrals in the rate-limiting nucleophilic-induced recyclization step.

Journal Article↗
PubMedDate not supplied

Study on the interaction between protein and Eu(III)-chlorotetracycline complex and the determination of protein using the fluorimetric method.

Chlorotetracycline (CTC) can react with europium ions Eu3+, and the complex emits the intrinsic fluorescence of Eu3+. The intensity is greatly enhanced by proteins and this forms the basis of a new fluorimetric method for determination of protein. Further research indicates that under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins, in the range 2.0 x 10(-7)-1.0 x 10(-5) g/mL for bovine serum albumin (BSA) (linear equation, I(f) = 34.35933 + 11.54467 x 10(6)C)(r = 0.99895) and 8.0 x 10(-7)-1.0 x 10(-5) g/mL for human serum albumin (HSA) (linear equation, I(f) = 76.58881 + 5.3569 x 10(6)C) (r = 0.99283). Detection limits (S/N = 3) were 8.9 x 10(-9) g/mL for BSA and 3.3 x 10(-8) g/mL for HSA. In an assay for BSA in calf serum, this method gave a value close to that determined by the UV spectrophotometric method.

Buffers↗
PubMedDate not supplied

Fluorescence enhancement effect of the morin-Al3+ -sodium dodecyl benzene sulphonate-protein system and the determination of proteins.

The fluorescence intensity of the morin-Al(3+) complex was greatly enhanced by proteins in the presence of sodium dodecyl benzene sulphonate (SDBS). Based on this, a new fluorimetric method for the determination of protein was developed. Under optimum conditions, the enhanced intensity of fluorescence was in proportion to the concentration of proteins in the range 1.0 x 10(-8)-1.3 x 10(-5) g/mL for bovine serum albumin (BSA), 4.0 x 10(-8)-1.2 x 10(-5) g/mL for egg albumin (EA) and 5.0 x 10(-8)-1.2 x 10(-5) g/mL for human serum albumin (HSA). Their detection limits (S:N = 3) were 5.0 x 10(-9), 1.8 x 10(-8) and 1.6 x 10(-8) g/mL, respectively. The interaction mechanism was also studied.

Aluminum↗
PubMedDate not supplied

The sensitive determination of nucleic acids using a fluorescence-quenching method.

Experiments indicated that nucleic acids can quench the fluorescence of the Eu3+ -2-thenoyltrifluoroacetone (TTA)-1,10-phenanthroline (Phen) system. Based on this, a sensitive method for the determination of nucleic acids was proposed. The experiments indicated that under the optimum conditions, the quenched fluorescence intensity was in proportion to the concentration of nucleic acids in the range 1.0 x 10(-11)-1.0 x 10(-6) g/mL for yeast RNA (yRNA), 5.0 x 10(-11)-5.0 x 10(-7) g/mL for fish sperm (fsDNA) and 1.0 x 10(-10)-1.5 x 10(-6) g/mL for calf thymus DNA (ctDNA). Their detection limits were 3.0 x 10(-12), 4.0 x 10(-12) and 5.0 x 10(-11) g/mL, respectively. Therefore, the proposed method is one of the most sensitive methods available. The interaction between nucleic acids and Eu3+ -TTA-Phen is also discussed.

Europium↗
PubMedDate not supplied

Circular dichroism spectra of regioregular poly[3 [(S)-2-methylbutyl]-thiophene] and of poly[3,4-di[(S)-2-methylbutyl]-thiophene].

Ultraviolet absorption and Circular Dichroism spectra in the region 300-700 nm for highly regioregular samples of Poly[3[(S)-2-methylbutyl]-thiophene] are reported for solutions in good and poor solvents, at variable temperature, and for films in various conditions. In the latter case novel CD data up to the melting temperature provide some hints for the self-assembling process towards supramolecular organization. UV-visible and CD data are also reported on the related polymer Poly[3,4-di[(S)-2-methylbutyl]-thiophene].

Journal Article↗
PubMedDate not supplied

Two new aromatic compounds from the resin of Styrax tonkinensis (Pier.) Craib.

Two new aromatic compounds, trans-(tetrahydro-2-(4-hydroxy-3-methoxyphenyl)-5-oxofuran-3-yl)methyl benzoate (1), 3-(4-hydroxy-3-methoxyphenyl)-2-oxopropyl benzoate (2) and one new natural product, 4-((E)-3-ethoxyprop-1-enyl)-2-methoxyphenol (3) together with five known aromatic compounds have been isolated from the resin of Styrax tonkinensis (Pier.) Craib. Their structures were determined by physical and spectroscopic methods.

Benzoates↗