检索结果-南通市图书馆

Acta Biochimica et Biophysica Sinica 2004年第12期36卷 840-844页

作者： Yapeng CHAO1.3, Shaoxiang XIONG2, Xiulan CHENG1. and Shijun QIAN1. 1.0} of Microbiology, Chinese Academy of Sciences,{1., china 2center of mass spectrometry, institute of chemistry, Chinese Academy of Sciences,{1., china 3Graduate School of the Chinese Academy of Sciences, beijing 1.0039, china institute of Microbiology Chinese Academy of SciencesBeijing 100080 China Graduate School of the Chinese Academy of Sciencesbeijing 1.0039 China center of {1. spectrometry Institute of Chemistry Chinese Academy of SciencesBeijing 100080 China

Heparinase from different sources can eliminate heparin or/and heparan sulfate into various low-molecular weight heparins with different characteristics. Porcine intestinal mucosa heparin was de- graded into a series of oligosaccharides by a novel heparinase from the species Sphingobacterium. Disaccha- ride components from the digests were separated and purified by ultrafiltration and HPLC. Five major peaks appeared as three types according to their retention time. The mass {1. of peak I mainly gave the non-sulfated disaccharide with the mass of 379 Da. Peak II and III were indicated as two major monosulfated disaccharides with molecular mass of 41. and 459 Da respectively. Moreover, the peak III represented an N- acetyl disaccharide. Both peak IV and V showed the same mass of 496 Da, hinting that they were disulfate- substituted disaccharides. No trisulfate-substituted disaccharides were detected in the mixture of the heparin digest though they were abundant in the heparin structure. The results revealed that the heparinase might specifically cut the sites with low sulfated domain in heparin.

关键词： electrospray ionization-mass {1. heparin disaccharides heparinase high perfor- mance liquid chromatography Sphingobacterium sp.

Explanation of the mechanism of carcinogenesis and syntheses of anticancer agents with high selectivity

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china {1. 2006年第1期49卷 44-62页

作者： DAI Qianhuan1.2 1. center of {1. and Bioengineering of Cancer Research, beijing Polytechnic University (Now known as beijing Univer-sity of Technology), beijing 1.0022, china 2. center of Environmental Sciences, Peking University, beijing 1.0871. china 1. center of {1. and Bioengineering of Cancer Research Beijing Polytechnic University Beijing 100022 China 2. center of Environmental Sciences Peking University Beijing 100871 China

In 1.79, the mechanism of chemical carcinogenesis, a challenging anddifficult scientific problem pending for a number of years, was explained by Dai Qianhuan. Themechanism named di-region theory predicted that a carcinogen always metabolizes to form a specialbi-functional alky-lating agent. This agent induces cross-linkages between the complementary basepairs in DMA and switches on initial mutageneses in genomes including point and frameshiftmutations. This, in turn, induces further deep mutageneses including the production of variouschimeric chromosomes, deletions and other aberrations found in genomes. In the end this initiatescarcinogenesis of the whole cell through the reverse transcription mechanism after a lengthyincubation period. Recently, this laboratory has verified that physical carcinogenesis, includingthe oncogenesis induced by radiation and asbestos as well as the carcinogenesis induced byendogenous factors such as estrogen or diethyl-stilbestrol switch on carcinogenesis by inducing theformation of cross-linkages between the complementary base pairs in DNA. Di-region theory has nowbeen supported by many experimental observations such as mutational spectra of various *** potential for carcinogenesis, teratogenesis, sterility and mutagenesis lumped together asgenetic toxicity appears to originate almost uniformly from the cross-linking between complementarybases, i.e. malignant cross-linking, which is in accordance with di-region theory. Other forms ofcross-linking between non-complementary bases, benign cross-linkings, show bi-functional alkylationanticancer activity but lack genetic toxicity. The predictable design and synthesis of a highselectivity anticancer agent with high efficacy and low genetic toxicity, a goal long pursued incancer chemotherapy, have been realized for the first time in this laboratory by inhibitingmalignant and heightening benign cross-linking using the principles of di-region theory. A series ofpatented new anticanc

关键词： mechanism of carcinogenesis, di-region theory, minoplatin, selectivity of anticancer agent, cross-linking between DNA bases, anticancer platinum complexes, predictive design of anticancer agent, second generation anticancer agent.

MB_8^(2-) (M=Be,Mg,Ca,Sr,and Ba):Planar octacoordinate alkaline earth metal atoms enclosed by boron rings

在线全文

学校读者我要写书评

暂无评论

Science china {1. 2010年第8期53卷 1737-1745,1829-1832页

作者： PU ZhiFeng1.GE MaoFa1.& LI QianShu2 1.tate Key Laboratory for Structural chemistry of Unstable and Stable Species {1. National Laboratory for Molecular Sciences (BNLMS) institute of chemistry,Chinese Academy of Sciences,{1. 1.01.0,china 2center for Computational Quantum chemistry,South china Normal University,Guangzhou 51.631.china 1. State Key Laboratory for Structural chemistry of Unstable and Stable Species beijing National Laboratory for Molecular Sciences (BNLMS) institute of {1. Chinese Academy of Sciences Beijing 100190 China2. Center for Computational Quantum Chemistry South China Normal University Guangzhou 510631 China

Complexes involving planar octacoordinate alkaline earth metal atoms in the centers of eight-membered boron rings have been investigated by two density functional theory (DFT) ***82-with D8h symmetry is predicted to be stable,both geometrically and electronically,since a good match is achieved between the size of the central beryllium atom and the eight-membered boron *** contrast,the other alkaline earth metal atoms cannot be stabilized in the center of a planar eight-membered boron ring because of their large *** following the out-of-plane imaginary vibrational frequency,pyramidal C8v MgB82-,CaB82-,SrB82-,and BaB82-structures are *** presence of delocalized π and σ valence molecular orbitals in D8h BeB82-gives rise to aromaticity,which is reflected by the value of the nucleus-independent chemical *** D8h BeB82-structure is confirmed to be the global minimum on the potential energy surface.

关键词： density functional theory octacoordinate alkaline earth metal aromatic molecular orbital

Photogeneration of the free radicals and singlet oxygen by chrysophanol from rheum

在线全文

学校读者我要写书评

暂无评论

Science china {1. 2004年第5期47卷 381-387页

作者： RAO Jing1.2, XIE Jie1. ZHAO Jingquan1.& ZHU Teng2 1. Key Laboratory of Photochemistry, {1. for Molecular Science, institute of chemistry, The Chinese Academy of Sciences, beijing 1.0080, china 2. University of Science and Technology beijing, beijing 1.083, china 1. Key Laboratory of Photochemistry Center for Molecular Science Institute of Chemistry The Chinese Academy of Sciences 100080 Beijing China 2. University of Science and Technology beijing 10083 Beijing China

In the current work, chryosphanol (MHAQ) was isolated and purified from rheum, and the photosensitization activities were studied. In nitrogen-saturated DMSO solution, irradia- tion of chryosphanol (MHAQ) with visible light (>430 nm) produced the semiquinone radical anions (MHAQ??), which was intensified significantly by an electron donor NADH, suggesting electron transfer between the excited and ground state photosensitizer molecules. In an air-saturated DMSO solution, superoxide radical anions (O2 ), trapped by DMPO, were detected. ?? It was proved that O2 was not originated from the singlet oxygen (1.2) but dependent on DMPO, ?? chrysophanol, oxygen and the irradiation time. The singlet oxygen and OH could also be pro- ? duced by the photosensitization of the photosensitizer. These suggest that chrysophanol pos- sesses the photosensitization activity via Type I mechanism and Type II mechanism. To evaluate the photosensitization activities of MHAQ, emodin and mixed anthraquinone derivatives ex- tracted from rheum, the relative productivities of O2 were estimated to be 1.8, 1.1.and 1.0 re- ?? spectively and the quantum yields for singlet oxygen to be 0.36, 0.53 and 0.1. respectively. Therefore, these low-cost pigments may be potentially used as phototherapeutic medicine for some kind of vascular diseases or photo-activated pesticides.

关键词： chrysophanol, ESR, semiquinone radical anions, superoxide radical anions, hydroxyl radical, singlet oxygen.

Research progress in synthesis and catalysis of polyoxometalates

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2005年第5期15卷 385-394页

作者： GONG Yun1. HU Changwen1.* and LIANG Hong2(1. Department of chemistry, School of Science, the {1. for Chemical Physics, beijing {1. of Technology, beijing 1.0081. china 2. Chemical Industry Press, beijing 1.0029, china) Department of chemistry School of Science the Institute for Chemical Physics Beijing Institute of Technology Beijing 100081 China Chemical Industry Press Beijing 100029 China

Recent progress in the synthetic chemistry and catalysis of polyoxometalates (POMs) is reviewed. The novel POMs and their derivatives emerging in nearly three years (2002—2004) are introduced, including POMs with novel structure, POMs-organic hybrid compounds and host-guest complexes. Our review is focused on the elaboration of POMs' supramolecular chemistry.

关键词： polyoxometalates hybrid host-guest structure supramolecule catalysis.

Theoretical study on thermal decomposition of azoisobutyronitrile in ground state

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china {1. 2004年第5期47卷 373-380页

作者： SUN Chengke1.2, ZHAO Hongmei1.& LI Zonghe1.1. Department of chemistry, {1. Normal University, {1. 1.0875, china 2. Department of chemistry, Qujing Normal College, Qujing 655000, china 1. Department of chemistry Beijing Normal University 100875 Beijing China 2. Department of chemistry Qujing Normal College 655000 Qujing China

The thermal decomposition mechanisms of azoisobutyronitrile (AIBN) in the ground state have been investigated systematically. Based on the potential energy surfaces (PES) of various possible dissociation paths obtained using the semiempirical AM1.method with partial optimization, the density function theory B3LYP/6-31.G* method was employed to optimize the geometric parameters of the reactants, the intermediates, the products and the transition states, which were further confirmed by the vibrational analysis. The obtained results show that the re- action process of the two-bond (three-body) simultaneous cleavage Me2(CN)C─ N=N─ C(CN)Me2? 2Me2(CN)C?+N2 is much more favorable than the reaction process of the two one- bond asynchronous cleavage Me2(CN)CN=N─C(CN)Me2 ? Me2(CN)CN=N?+ Me2(CN)C?? Me2(CN)C?+ N2. It was suggested that the electron shrinking effect of double bond (─N=N─) in AIBN and the stabilities of the Me2(CN)C?radical as well as N2 molecule are main factors of leading to the reaction proceeding in the former pathway. The calculation results were consistent with all the experimental facts.

关键词： azoisobutyronitrile, radicals, thermal decomposition, density function theory (DFT).

Local and non-local sources of airborne particulate pollution at beijing——The ratio of Mg/Al as an element tracer for estimating the contributions of mineral aerosols from outside beijing

在线全文

学校读者我要写书评

暂无评论

Science china {1. 2005年第3期48卷 253-264页

作者： HAN Lihui1. ZHUANG Guoshun1.2,3, SUN Yele1.& WANG Zifa3 1. The center for Atmospheric Environmental Study, Department of {1., beijing Normal University, beijing 1.0875, china 2. center for Atmospheric {1. Study, Department of Environmental Science & Engineering, Fudan University, Shanghai 200433, china 3. LAPC/NZC, institute of Atmospheric Physics, CAS, beijing 1.0029, china 1. The center for Atmospheric Environmental Study Department of Chemistry Beijing Normal University 100875 Beijing China 2. center for Atmospheric {1. Study Department of Environmental Science & Engineering Fudan University 200433 Shanghai China 3. institute of Atmospheric Physics CAS LAPC/NZC 100029 Beijing China

A new element tracer technique has firstly been established to estimate the contri-butions of mineral aerosols from both inside and outside beijing. The ratio of Mg/Al in aerosol is a feasible element tracer to distinguish between the sources of inside and outside beijing. Mineral aerosol, inorganic pollution aerosol mainly as sulfate and nitrate, and organic aerosol are the major components of airborne particulates in beijing, of which mineral aerosol accounted for 32%―67% of total suspended particles （TSP）, 1.%―70% of fine particles （PM2.5）, and as high as 74% and 90% of TSP and PM2.5, respectively, in dust storm. The sources from outside beijing contributed 62% （38%―86%） of the total mineral aerosols in TSP, 69% （52%―90%） in PM1., and 76% （59%―93%） in PM2.5 in spring, and 69% （52%―83%）, 79% （52%―93%）, and 45% （7%―79%） in TSP, PM1., and PM2.5, respectively, in winter, while only20% in summer and autumn. The sources from outside beijing contributed as high as 97% during dust storm and were the dominant source of airborne particulates in beijing. The contributions from outside Bei-jing in spring and winter are higher than those in summer, indicating clearly that it was related to the various meteorological factors.

关键词： mineral aerosol local sources non-local sources dust storm re-suspended dust element tracer technique.

Theoretical study on the reaction mechanism of (CH3)3CO(.) radical with NO

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Science china {1. 2004年第4期47卷 289-294页

作者： ZHAO Hongmei1.2, LIU Kun1. SUN Chengke1.& LI Zonghe1.1. Department of chemistry, {1. Normal University, {1. 1.0875, china 2. Department of chemistry, Beihua University, Jilin 1.201., china 1. Department of chemistry Beijing Normal University 100875 Beijing China 2. Department of chemistry Beihua University 132013 Jilin China

The reaction mechanism of (CH3)3CO? radical with NO is theoretically investigated at the B3LYP/6-31.* level. The results show that the reaction is multi-channel in the single state and triplet state. The potential energy surfaces of reaction paths in the single state are lower than that in the triple state. The balance reaction: (CH3)3CONO(CH3)3CO?+NO, whose potential energy surface is the lowest in all the reaction paths, makes the probability of measuring (CH3)3CO? radical increase. So NO may be considered as a stabilizing reagent for the (CH3)3CO? radical.

关键词： (CH3)3CO. radical DFT reaction mechanism NO

Fluorescence response of hypocrellin B to the environmental changes in a mimic biological membrane——liposome

在线全文

学校读者我要写书评

暂无评论

Science china {1. 2004年第4期47卷 335-339页

作者： JIN Xuanye1.2, ZHAO Yuewei1. XIE Jie1.& ZHAO Jingquan1.1. CAS Key Laboratory of Photochemistry, {1. for Molecular Science, institute of chemistry, Chinese Academy of Science, beijing 1.0080, china 2. School of Earth Sciences and Resources, china University of Geosciences, beijing 1.0083, china 1. CAS Key Laboratory of Photochemistry Center for Molecular Science Institute of Chemistry Chinese Academy of Science 100080 Beijing China 2. School of Earth Sciences and Resources China University of Geosciences 100083 Beijing China

Liposome is well known as not only a drug-delivery system but also a simple model for biological membranes. It was reported that fluorescence properties of hypocrellins were changeable over some extreme pH values. In the current work, the effects of the microenvironments on the fluorescence properties of HB in liposome, including approximately physiological range of pH values pH = 6.0-8.0, concentration of cholesterols and ionic strength of the solution, were studied. It was found that the fluorescence intensity of HB was sensitive to and also regulated by the microenvironments. When concentration of cholesterols and ionic strength keep invariable in PBS solution, there exists the maximum for the fluorescence of HB-liposome at pH 7.4 while the minimum for that of HB at pH 7.0. In addition, when pH value keeps constant (7.2), there exists the maximum at the ionic strength of 0.1. mol/kg while that at the concentration of 6×1.?4 mol/L for cholesterols. On the other hand, in PBS solution, the lower the ionic strength is, the higher the fluorescence intensity is. The environment-sensitive fluorescence may be potentially applicable to probe some specific environmental features in cells or tissues.

关键词： microenvironment hypocrellin B liposome fluorescence

Comparative study of the effect of Cu_2O and MoO_3 on flame retardance and smoke emission of PVC by Cone and TGA

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 1998年第13期43卷 1090-1094页

作者： LI Bin\+1.and WANG Jianqi\+2 1. Department of chemistry, Northeast Forestry University, Harbin 1.0040,{1. 2. National Laboratory of Flame Retardant Materials, beijing institute of Technology, beijing, 1.0081.{1. Department of chemistry Northeast Forestry University Harbin China National Laboratory of Flame Retardant Materials Beijing Institute of Technology Beijing China

Cuprous and molybdic oxides exhibit extremely effectiveness in smoke suppression for PVC. However, few are the data reported concerning flame retardance and smoke emission of PVC taken from Cone calorimetry relative to the conventional thermal analysis technique. Abundant data from Cone calorimetry have been acquired. Data analysis was achieved through the study of MLR, HRR, SEA tested at irradiance of 25 kWm -2 . The understandable flame retardance of PVC/Cu\-2O and PVC/MoO\-3 relative to pure PVC has been rationalized by their lowered heat release rates and enhanced char residues. The difference in smoke reduction between these two oxides consists in the time scale. As clearly seen under air atmosphere both oxides exert themselves to the afterglow which has been recognized as a dangerous source, in particular in the full_scale fire situation.

关键词： cone calorimetry poly(vinyl chloride) flame retardation smoke emission cuprous oxide molybdic oxide.