Showing papers by "Xiamen University published in 2001"

Antitumor and antifungal activities in endophytic fungi isolated from pharmaceutical plants Taxus mairei, Cephalataxus fortunei and Torreya grandis

Abstract: The purpose of this work was to screen the endophytic fungi having antitumor or antifungal activity, which were isolated from the inner barks of three kinds of pharmaceutical plants, Taxus mairei, Cephalataxus fortunei and Torreya grandis, collected from Fujian province, China. Antitumor activity was studied by the MTT assay and antifungal activity was determined by observing fungal growth inhibition. 13.4% of endophytic fungi fermentation broths displayed cytotoxic activity on HL-60 cells at and below a dilution of 1:50, and 6.4% on KB cells. 52.3% of endophytic fungi fermentation broths displayed growth inhibition on at least one pathogenic fungi, such as Neurospora sp., Trichoderma sp. and Fusarium sp. Among all endophytic fungi isolated, the genus Paecilomyces sp. has the highest positive rate of antitumor and antifungal activity. These results indicate that endophytic fungi could be a promising source for antitumor and antifungal bioactive agents.

Extracellular matrix protein 1 (ECM1) has angiogenic properties and is expressed by breast tumor cells

Abstract: Tumor growth and metastasis are critically dependent on the formation of new blood vessels. The present study found that extracellular matrix protein 1 (ECM1), a newly described secretory glycoprotein, promotes angiogenesis. This was initially suggested by in situ hybridization studies of mouse embryos indicating that the ECM1 message was associated with blood vessels and its expression pattern was similar to that of flk-1, a recognized marker for endothelium. More direct evidence for the role of ECM1 in angiogenesis was provided by the fact that highly purified recombinant ECM1 stimulated the proliferation of cultured endothelial cells and promoted blood vessel formation in the chorioallantoic membrane of chicken embryos. Immunohistochemical staining with specific antibodies indicated that ECM1 was expressed by the human breast cancer cell lines MDA-435 and LCC15, both of which are highly tumorigenic. In addition, staining of tissue sections from patients with breast cancer revealed that ECM1 was present in a significant proportion of primary and secondary tumors. Collectively, the results of this study suggest that ECM1 possesses angiogenic properties that may promote tumor progression.

Chemisorption and Decomposition of Thiophene and Furan on the Si(100)-2 × 1 Surface: A Quantum Chemical Study

Abstract: The chemisorption and decomposition of thiophene (C4H4S) and furan (C4H4O) on the reconstructed Si(100)-2 × 1 surface has been investigated by means of the hybrid density functional (B3LYP) method in combination with a cluster model approach. Two chemisorption mechanisms, i.e., [4 + 2] and [2 + 2] cycloadditions of C4H4X (X = S,O) onto a surface dimer site, have been considered comparatively. The calculations revealed that the former process is barrierless and favorable over the latter, which requires a small activation energy (2.6 kcal/mol for thiophene and 1.2 kcal/mol for furan). The di-σ bonded surface species formed by [4 + 2] cycloaddition-type chemisorption can either undergo further [2 + 2] cycloaddition with a neighboring SiSi dimer site, giving rise to a tetra-σ bonded surface species, or undergo deoxygenation (desulfurization) by transferring the heteroatom to a neighboring SiSi dimer site, leading to a six-member ring metallocyclic C4H4Si2 surface species. The latter process was found to be sl...

Electrolytic hydride generation (EC-HG)—a sample introduction system with some special features

Abstract: Fundamental aspects of electrolytic hydride generation (EC-HG) and the application of EC-HG as a sample introduction system in atomic spectrometry are presented One of the aims of this review is to help the analyst to select the most suitable electrolytic hydride generator and diverse operating parameters, and especially the choice of the cathode material, in relation to the requirements of the analytical problem The application of EC-HG in speciation analysis of hydride-forming elements is one of the topics of this review Additionally, the use of EC-HG is critically evaluated as an alternative to wet chemical hydride generation

Conformational antigenic determinants generated by interactions between a bacterially expressed recombinant peptide of the hepatitis E virus structural protein

Abstract: A 23 kDa peptide locating to amino acid residues 394 to 604 of the major Hepatitis E Virus (HEV) structural protein was expressed in E. coli. This peptide was found to interact naturally with one another to form homodimers and it was recognized strongly and commonly in its dimeric form by HEV reactive human sera. The antigenic activity associated with the dimeric form was abrogated when the dimer was dissociated into monomer and the activity was reconstituted after the monomer was re-associated into dimer again. The dimeric form of the peptide elicited a vigorous antibody response in experimental animals and the resulting antisera were found to cross-react against HEV, effecting an efficient immune capture of the virus. These results attributed the antigenic activity associated with the dimeric form of the peptide to conformational antigenic determinants generated as a result of interaction between the peptide molecules. It is suggested that some of these antigenic determinants may be expressed by the HEV capsid and raised the possibility of this bacterially expressed peptide as an HEV vaccine candidate.

Adsorption of methanol, formaldehyde and formic acid on the Si(100)-2 × 1 surface: A computational study

Abstract: The adsorption of methanol, formaldehyde and formic acid on the Si(100)-2 × 1 surface have been investigated by means of first-principles density functional cluster model calculations and ab initio ONIOM calculations. The dissociative adsorption of methanol on the Si(100) surface takes place readily, giving rise to Si–OCH3 and Si–H surface species. The reaction, occurring barrierlessly ia a stable chemisorbed state and the transition state for dissociation, is highly exothermic. The chemisorption of formaldehyde on the Si(100) surface is also barrierless and exothermic with the formation of a 4-member ring –SiCOSi– surface species. This result indicates that the carbonyl (CO) group can undergo cycloaddition onto the Si dimer on the Si(100) surface. The dissociative chemisorption of formic acid occurs readily on the Si(100) surface with the formation of unidentate formate surface species and H adatoms. Its exothermicity is higher than 60 kcal mol−1. The vibrational frequencies of the surface species produced by the chemisorption of the three C1 molecules have been calculated and compared with the available experimental data.

A unique open inorganic-organic framework with alternate hexa- and penta-coordinate cobalt(II) sites Synthesis, crystal structure and magnetic properties of Co-3(C4H4O4)(25)(OH) (n)center dot 05nH(2)O

Abstract: A three-dimensional open-framework with unprecedented alternate hexa- and penta-coordinate cobalt(II) sites was obtained from the hydrothermal reaction of cobalt nitrate and succinate in a basic solution. Of the four crystallographically independent Co(II) atoms in the crystal structure of this compound, three are hexa-coordinated and one penta-coordinated. The cobalt(II) atoms are linked by edge-sharing CoOn (n = 5 or 6) polyhedrons. The temperature dependence of the magnetic susceptibility of this compound shows strong antiferromagnetic interaction between the metal atoms.

Bioaccumulation of mercury from wastewater by genetically engineered Escherichia coli.

Abstract: Genetically engineered E. coli, which express both a Hg2+ transport system and metallothionein, were tested for their ability to remove mercury from wastewater. The wastewater contained more than ten different ions, including 2.58 mg/l mercury, and its pH was 9.6. Mercury uptake was faster from the wastewater than from distilled water, probably because of the higher ionic strength, as the high pH had little effect on mercury accumulation. EDTA also stimulated mercury uptake rather than inhibiting it. A hollow-fiber bioreactor was used to retain induced cells for continuous mercury uptake. The cells removed more than 99% of the mercury in the wastewater and the final amount of mercury accumulated was 26.8 mg/g cell dry weight, while none of the other ions were removed from the water. These results indicated that the induced cells had a high affinity and specificity for mercury.

Oxidative Dehydrogenation of Propane over Mesoporous HMS Silica Supported Vanadia

Abstract: Vanadium-containing mesoporous HMS catalysts have been prepared and characterized for the oxidative dehydrogenation (ODH) of propane. It is demonstrated that the vanadium supported HMS catalysts exhibit a much higher catalytic activity than the literature results obtained over the vanadium supported MCM-41 catalysts in the ODH of propane. The improved catalytic activity of the V-HMS catalysts has been attributed to the presence of high concentration of well-dispersed vanadium species on the surface of the mesoporous HMS materials.

Determination of degree of substitution for N-acylated chitosan using IR spectra

Abstract: Chitosans with various degrees of deacetylation (D.D.), which were used as standard sample for FTIR determination, were prepared from completely deacetylated chitosan by homogeneous N-acetylation reaction. By combining four probable probe bands, i.e. 1655, 1560, 1380 and 1320 cm−1, eight probable reference bands, i.e. 3430, 2920, 2880, 1425, 1155, 1070, 1030 and 895 cm−1 and two baseline methods, the most suitable ratiosA probe band/A reference band from IR spectra to determine the degree of acetylation of chitosan were evaluated from 48 combinations to beA 1560/A 2880,A 1560/A 2920 andA 1655/A 3430(A 1560/A 2880 is mostly recommended). The second baseline method, i.e. linking between adjacent two valleys, was better for measuring the absorbances of 1560 and 1655 cm?1 bands. The determination range of the D.D. (1%–100%) covered almost the whole range. The standard curves withA 1560/A 2880 andA 1655/A 3430were also suitable for the determination of degree of substitution of other N-acylated chitosan, such as N-propionyl chitosan, N-butyryl chitosan and N-hexanoyl chitosan.

Colloidal organic carbon and 234 Th in the Gulf of Maine

Abstract: The role of colloids in the biogeochemical cycling of organic carbon and 234 Th was examined in the Gulf of Maine Ž. during the summer of 1996 and 1997. The colloidal fraction was separated using a 1 kiloDalton kDa cross-flow Ž. ultrafiltration CFF membrane. The mass balance of CFF was carefully checked in order to evaluate the performance of the Ž. CFF system, since this is one of the primary concerns when using CFF methods. For bulk organic carbon OC , the Ž. membrane showed excellent recoveries 94–107% as long as preconditioning techniques were employed. Although our 234 Ž. mass balances for Th were higher than previous efforts ) 55% for most samples , significant losses still occurred. Furthermore, a large percentage of the AlostB 234 Th was irrecoverable even after the CFF membranes were cleaned with weak acid and base rinses. Ž. The colloidal organic C COC represented 16–25% of the organic carbon pool, and was correlated with the Chl a fluorescence maximum. The profile of colloidal 234 Th, 7–36% of the total 234 Th, followed a similar pattern. The difference between the mass balances for 234 Th and OC suggests that 234 Th may follow only a fraction of COC within the water column. This fraction appears to be the more reactive component of the COC pool. Given the higher and more consistent 234 Th recoveries found using our CFF techniques, we were able to constrain the turnover rate of COC to between 3 and 30 days. Turnover rates of dissolved and particulate OC varied from 14 to 41 and 19 to 68 days, respectively. q 2001 Elsevier Science B.V. All rights reserved.

3~6 Months Variation of Sea Surface Height in the South China Sea and Its Adjacent Ocean

Abstract: Sea surface height (SSH) variations with a period of 3≈6 months (SSH36 variations) in the South China Sea (SCS) and its adjacent ocean are intensively investigated using six years of TOPEX/POSEIDON-derived SSH data. The results show that there appears higher energy of SSH36 variations in the east of the Luzon Strait and in some areas of the SCS, both of which are correlated with each other. The SSH36 variations usually propagate westward in the subtropical region of the northern Pacific Ocean and turn northward in the east of the Luzon Strait while they sometimes propagate into the SCS through the Luzon Strait with the phase speed of about 11–12 cm/s, which may be considered as Rossby waves. It can be inferred that the SSH36 variations are strongly associated with current structures and eddies in the SCS because of their significant intensiveness. The SSH variations with the period of 6 months are more dominant than those with the other periods in the SCS.

Fe(II)–EDTA chelate-induced aromatic hydroxylation of terephthalate as a new method for the evaluation of hydroxyl radical-scavenging ability

Abstract: The investigation of Fe(II)–EDTA chelate-induced aromatic hydroxylation of terephthalate in pH 7.4 phosphate buffer solution and a new method for the evaluation of hydroxyl radical-scavenging ability are reported. The method is based on attack of the hydroxyl radical on the terephthalate to produce highly fluorescent 2-hydroxyterephthalate, which is detected fluorimetrically. The formation of hydroxyl radical is believed to be the result of the reduction of molecular oxygen by Fe(II)–EDTA to form superoxide radical, which in turn dismutates to hydrogen peroxide, and then Fe(II)–EDTA catalyzes the decomposition of hydrogen peroxide to produce hydroxyl radical. The mechanism of the generation of hydroxyl radical in the proposed system was confirmed. This study established a simple and inexpensive method for the evaluation of the scavenging ability of some compounds on hydroxyl radicals.

Investigation of the anthracene-nitroxide hybrid molecule as a probe for hydroxyl radicals.

Abstract: A new method for the determination of hydroxyl radicals is proposed. The method is based on the use of a hybrid molecule consisting of a fluorescent chromophore, anthracene, and a nitroxide radical. In the hybrid molecule, the nitroxide quenches the fluorescence of anthracene strongly. The reaction of hydroxyl radicals with dimethyl sulfoxide generates quantitatively methyl radicals, which then combine with the nitroxide moiety of the hybrid molecules to result in an increase in the fluorescence intensity. The fluorescence increase is proportional to the concentration of hydroxyl radicals. The proposed method is capable of detecting hydroxyl radicals generated in the Fenton system. It is a simple and sensitive technique for the determination of hydroxyl radicals.

H-1 MAS NMR spectra of hydroxyl species on diatomite surface

Abstract: High spinning speed1H magic-angle spinning nuclear magnetic resonance (1H MAS NMR) was used to detect surface hydroxyl groups of diatomite, which include isolated hydroxyl groups and hydrogen-bonded hydroxyl groups, and water adsorbed on diatomite surface that include pore water and hydrogen-bonded water. The corresponding proton chemical shifts of above species are ca. 2.0, 6.0–7.1, 4.9 and 3.0 respectively. Accompanied by thermal treatment temperature ascending, the pore water and hydrogen-bonded water are desorbed successively. As a result, the relative intensities of the peaks assigned to protons of isolated hydroxyl groups and hydrogen-bonded hydroxyl groups increase gradually and reach their maxima at 1000°C. After 1100°C calcination, the hydroxyl groups that classified to strongly hydrogen-bonded ones and the isolated hydroxyl groups condense basically. But some weakly hydrogen-bonded hydroxyl groups may still persist in the micropores.