Chemical Research in Chinese Universities最新文献

This article focuses on iodine determination by microwave plasma torch atomic emission spectrometry (MPT-AES) coupled with online preconcentration vapor generation method. A new desolvation device, multistrand Nafion dryer, was used as the substitute for condenser desolvation system. Some experimental conditions, such as preconcentration time, acidity of sample solution, rinsing solution acidity and dynamic linear range were investigated and optimized. The new desolvation system eliminates the problem of decreasing emission intensity of I(I) 206.238 nm line with the increase of working time on a conventional condenser desolvation system, thus greatly improving the reproducibility.

In this study, the process of a biodegradable polylactide(PLA) microsphere encapsulating ginsenoside Rg3 was first studied by the emulsion solvent evaporation method, for enhancing solubility and stability of ginsenoside Rg3. Alabum was also first used as a modifier in this method. The mean diameter of the prepared PLA microspheres containing Rg3 was 40 μm. Ginsenoside Rg3 released from the microspheres was studied by HPLC and detected by UV. It was found that the drug release curve fitted the Model Heller-Baker best.

A new heterometallic 4f-3d complex [Y(C₆NO₂H₅)₃(H₂O)₂]n(1.5nZnCl₄). nH₂O(1), was synthesized via a hydrothermal reaction and structurally characterized. Complex 1 crystallized in the monoclinic system with space group P2₁/c: a=0.94847(9) nm, b=2.0947(2) nm, c=1.6001(2) nm, β=104.467(2)°, V-3.0781(5) nm³, M_r=823.04, D_c=1.776 g/cm³, S=1.009, μ(Mo Kα)=3.603 mm⁻¹, F(000)=1632, R=0.0787, and wR=0.2273. Complex 1, with four formula units in a cell, was characteristic of a one-dimensional polycationic chain-like structure. Photolumincscent investigation showed that the title complex displayed a strong emission in the blue region, which was attributed to the intraligand π-π^* transition of the nicotinic ligands. Optical absorption spectrum of complex 1 revealed the presence of a wide optical bandgap of 4.17 eV.

Poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene](MEH-PPV) solutions with different concentrations were prepared in chloroform for different ultrasonication times. The ultraviolet absorption and photoluminescence(PL) spectra of the MEH-PPV solutions were measured, and the electronic states of the polymer chains under different experimental conditions were studied. The results showed that the effects of ultrasonication on the dilute and concentrated solutions were different. After ultrasonication, the intensity of the absorption peak at 280 nm significantly decreased, relative to the absorption peak at 500 nm for both dilute and concentrated solutions, indicating that the proportion of the two excited states in the polymer chains had changed. For dilute MEH-PPV solutions, the blue-shifted absorption(at about 500 nm) and PL spectra show that ultrasonication also led to polymer chain degradation and thus shortened the effective conjugation length. For concentrated solutions, however, the peak positions of the absorption spectra remained unchanged. In addition, the effects of the solution temperatures on the optical spectra for the MEH-PPV solutions were also discussed.

Pig pancreas ferritin(PPF) was purified by ultra-centrifugation, ion-exchange chromatography, and native gradient polyacrylamide gel electrophoresis(PAGE_NG). Sodium dodecyl sulfate(SDS)-PAGE indicates that PPF consists of two subunit types, namely, H(21000) and L(19000) subunits, and its core shows an average element composition of 1698 Fe³⁺ and 179 phosphate molecules within the hollow shell, giving a 9.5:1 ratio of Fe³⁺ to phosphate. An off line approach combining reversed-phase high-performance liquid chromatography(RP-HPLC) with matrix-assisted laser desorption ionization time of flight mass spectrometry(MALDI-TOF MS) made the decomposition of PPF shell into H and L subunits for the analysis of mass spectrometry(MS), giving molecular weights of both H(21014.4) and L(18319.9) subunits. Both subunit types were further identified by an approach combining peptide mass fingerprint(PMF) with database search. A ratio of 1H to 2L subunits in PPF was determined by SDS-PAGE, RP-HPLC, and MALDI-TOF MS, respectively. It is well known that the non-covalent interaction of L-L or H-L subunits is stronger than that of H-H subunits in PPF, which may be further used to explain the unclear physiological function between H and L subunits in PPF.

Catalytic oxidation of NO by O₂ over La_0.8Sr_0.2MnO₃ was tested in a tubular reactor. The reaction temperature ranged from 373 to 473 K, space time from 0.090 to 0.720 s, inlet NO concentration from 300 to 2000 μL/L, and O₂ volume fraction from 3% to 9%. The steady-state conversion of NO was increased significantly with increasing reaction temperature and the space time, slightly with increasing the O₂ concentration but decreased with increasing the inlet NO concentration at a lower temperature. Under the conditions of 0.720 s space time, 500 μL/L NO concentration, 5% O₂ volume fraction and 473 K, NO conversion reached 90%. A kinetic model including a network of 12 elementary reactions with the desorption of NO₂ as the rate-limiting step is established and fits the experimental data well. The activation energy of NO₂ desorption from the catalyst surface is determined to be 101 kJ/mol.

Several borohydride reagents: sodium borohydride, sodium cyanoborohydride, soudium acetoxyborohydride and soudium triacetoxyborohydride were screened, respectively, for the reduction of 7-demethylsinomenine, which was an α,β-dicarbonyl compound derived from sinomenine. Highly regio- and stereo-selectivity was acquired when sodium cyanoborohydride or NaBH(OAc)₃ was used. The product was structurally confirmed as 7R configuration by NMR, X-ray crystal diffraction analysis. Some preliminary discussion was also made on the mechanism of the selective reduction.

The crude polysaccharide was obtained by means of the decolorization of porphyrized Cordyceps minlitaris stroma with organic solvent, extraction with hot water, precipitation in 80% ethanol, and protein removal with the Sevag method. After purification with Sephadex G-75, two of its components, CMP-1 and CMP-2, were obtained. Through the assay of gel chromatography and polarimetry, CMP-1 was identified as pure polysaccharide. The results demonstrated that CMP-1 had favorable oxidation resistance activity, which could scavenge not only oxygen-free radicals in the self-oxidation system of pyrogallic acid, but also the hydroxide-free radicals in the Fenton system. The study focused on the effects of low, medium, and high dosages of CMP-1 in rat blood serum on the proliferation of glomerular mesangial cells in vitro. Through MTT Colorimetric analysis, the activities were compared among the blank control group and the Niaoduqing positive control group CMP-1 and CMP-2. The results shows that CMP-1 was able to inhibit the proliferation of rat glomerular mesangial cells effectively. Therefore, CMP-1, one component of polysaccharides of Cordyceps minlitaris, was certainly a potential remedy for hyperplastic glomerular nephritis, whose antioxidant activity could slow down the process of chronic renal failure(CRF) to some extent.

Recent observations indicate that the resistance of apoptosis is an important process of tumor metastasis and metastases are the cause of 90% of human cancer death. Etoposide, a semisynthetic derivative of the podophyllotoxins, is a clinically used anti-cancer reagent, but the effects of it on metastatic gastric carcinoma cells are totally unknown. In this study, etoposide induced apoptotic cell death in human gastric adenocarcinoma cell line SGC-7901, derived from metastatic lymph nodes, as evidenced by the analysis of DNA fragmentation, apoptotic body formation, caspase activation, and apoptosis specific changes in cell morphology is demonstrated. The depolarization of mitochondrial membrane and the release of cytochrome c were most early events in etoposide treated SGC-7901 cells, and were followed by caspase-3 activation and PARP cleavage. Caspase-8 activation was not detected under the same condition. Thus, it was proposed that etoposide induces caspase-associated apoptotic cell death in human metastatic gastric carcinoma, which is initiated by mitochondrial cytochrome c release.

Low-temperature heat capacities of the solid compound Zn(C₄H₇O₅)₂(s) were measured in a temperature range from 78 to 374 K, with an automated adiabatic calorimeter. A solid-to-solid phase transition occurred in the temperature range of 295—322 K. The peak temperature, the enthalpy, and entropy of the phase transition were determined to be (316.269±1.039) K, (11.194±0.335) kJ·mol^-1, and (35.391±0.654) J·K^-1·mol^-1, respectively. The experimental values of the molar heat capacities in the temperature regions of 78—295 K and 322—374 K were fitted to two polynomial equations of heat capacities(C_p,m) with reduced temperatures(X) and [X = f(T)], with the help of the least squares method, respectively. The smoothed molar heat capacities and thermodynamic functions of the compound, relative to that of the standard reference temperature 293.15 K, were calculated on the basis of the fitted polynomials and tabulated with an interval of 5 K. In addition, the possible mechanism of thermal decomposition of the compound was inferred by the result of TG-DTG analysis.