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971.
972.
Yuqin Yao Zhihui Cheng Haoyu Ye Yongmei Xie Jing He Minghai Tang Tao Shen Jiangman Wang Yan Zhou Zejun Lu Feng Luo Lijuan Chen Luoting Yu Jin‐Liang Yang Aihua Peng Yuquan Wei 《Journal of separation science》2010,33(9):1331-1337
Ansamitocin P‐3 is a potent anti‐tumor maytansinoid found in Actinosynnema pretiosum. However, due to the complexity of the fermentation broth of Actinomycete, how to effectively separate ansamitocin P‐3 is still a challenge. In this study, both analytical and preparative high‐performance counter‐current chromatography were successfully used to separate and purify ansamitocin P‐3 from fermentation broth. A total of 28.8 mg ansamitocin P‐3 with purity of 98.4% was separated from 160 mg crude sample of fermentation broth in less than 80 min with the two‐phase solvent system of hexane–ethyl acetate–methanol–water (0.6:1:0.6:1, v/v/v/v). The purity and structural identification were determined by HPLC, 1H NMR, 13C NMR and mass spectroscopy. 相似文献
973.
A novel PEGylated biodegradable hyperbranched PEG‐b‐PDMAEMA has been synthesized. The low toxicity, small molecular weight PDMAEMA chains were crosslinked using a biodegradable disulfide‐based dimethacrylate (DSDMA) agent to yield higher molecular weight hyperbranched polymers. PEG chains were linked onto the polymer surface, masking the positive charge (as shown by Zeta potential measurements) and reducing the toxicity of the polymer. The hyperbranched structures were also cleaved under reducing conditions and analyzed, confirming the expected component structures. The hyperbranched polymer was mixed with DNA and efficient binding was shown to occur through electrostatic interactions. The hyperbranched structures could be reduced easily, generating lower toxicity oligomer chains.
974.
Lei Zhang Qingqing Li Wei Tao Bohao Yu Yiping Du 《Analytical and bioanalytical chemistry》2010,398(4):1827-1832
Silver sol surface-enhanced Raman spectroscopy (SERS) was considered as a technique in the quantitative analysis of low-concentration thymine. Because of the poor stability and reproducibility of SERS signal, a polymer of polyacrylic acid sodium was selected as a stable medium to add into silver sol in order to obtain a surface-enhanced Raman spectroscopy signal. Assignments of Raman shift for solid thymine, SERS of thymine, and SERS of thymine containing stable medium were given. The comparison of Raman peaks between them showed that the addition of stable medium had a little influence on the SERS of thymine and is suitable for the quantitative analysis of low-concentration thymine. 相似文献
975.
Tianmin Shu Junchen Wu Ying Zou Keyin Liu Liqing Chen Tao Yi 《Frontiers of Chemistry in China》2010,5(2):184-192
A novel type of ligands contained 1,4,7,10-tetrazacyclododecane and functionalized by two azobenzene moieties grafted with
two alkyl chains was designed and synthesized. The ligands with long alkyl chains can form metallogels in the presence of
Zn2+ cations. The formation of metallogel was followed by NMR and electronic spectral detection. The morphology of the xerogels
is varied with the equivalent of Zn2+ cations and the concentration of the gel. Spectral and structural analysis indicated that the driving forces of the gel formation
were attributed to intermolecular hydrophobic interactions between alkyl chains and π-π interaction between azobenzenes. 相似文献
976.
Tao Jiang Fei Du Kejin Zhang Yingjin Wei Zhe Li Chunzhong Wang Gang Chen 《Solid State Sciences》2010,12(9):1672-1676
Carbon coated and carbon free Li3V2(PO4)3 cathode materials were prepared by carbothermal reduction and H2 reduction methods, respectively. The carbon free material had a grain size about 1 μm whereas the carbon coated material was less than 100 nm. The surface carbon layer enhanced the electronic conductivity of Li3V2(PO4)3 by five orders of magnitude. In addition, the surface carbon layer also prevented the formation of SEI film, decreased the charge transfer resistance and increased the chemical diffusion coefficient of Li+ ions. All of these advantages improved the electrochemical performance of Li3V2(PO4)3. As most of intercalation materials, the low temperature performance of Li3V2(PO4)3 was poorer than that at room temperature. This was attributed to the electrochemical sluggish kinetics which caused higher charge transfer resistance and smaller chemical diffusion coefficient. The carbon coating technique was effective to eliminate these sluggish kinetics, and then improved the low temperature performance of Li3V2(PO4)3. 相似文献
977.
Cobalt catalysts supported on a series of mesoporous SBA-15 materials isomorphically substituted with zirconium (Zr/Si atomic ratio = 1/20) with different pore sizes (5.7 nm, 7.8 nm, 11.6 nm, 17.6 nm) have been synthesized. The catalysts were characterized by transmission electron microscopy, 29Si solid state magic angle spinning (MAS) NMR, N2 adsorption-desorption measurements, X-ray powder diffraction, X-ray photoelectron spectroscopy, H2-temperature programmed reduction, H2-temperature programmed desorption and O2 titrations. The results indicated that larger pore size led to weaker interactions between cobalt and the supports which lowered the temperature of both reduction steps (Co3O4→CoO and CoO→Co0). The catalytic performances of the catalysts in Fischer-Tropsch synthesis (FTS) were tested in a fixed bed reactor. It was found that the FTS catalytic activity and product selectivity depended strongly on the pore size of the catalysts. The catalyst with a pore size of 7.8 nm showed the best FTS activity, and the catalyst with a pore size of 17.6 nm showed the highest selectivity to C12–C20 and C20+ hydrocarbons. 相似文献
978.
The slightly water-soluble anticancer drug camptothecin (CPT) and its inclusion complexes with cucurbit[n = 7, 8]uril (Q[n] (n = 7, 8)) were investigated. The formation of 1:2 complexes with Q[n] (n = 7, 8) in aqueous solution was confirmed by fluorescence spectroscopy and the apparent stability constants were determined to be higher than 3.01 × 1012 L2/mol2. The solid inclusion complexes of CPT and Q[n] (n = 7, 8) were also prepared by the co-evaporation method and characterized by Fourier transformation-infrared spectroscopy, differential scanning calorimetry and powder X-ray diffraction. Aqueous solubility and dissolution studies indicate that the complexes exhibited significantly increased dissolution rates compared with the pure drug and physical mixtures. The potential of Q[7] or Q[8] for stabilizing lactone modality of CPT was investigated by the High Performance Liquid Chromatography (HPLC) method. The results reveal more than 63% CPT lactone form (active form) in CPT-Q[7] or Q[8] complexes compared to only 36% CPT lactone form in the absence of Q[7] or Q[8] after being incubated in the phosphate buffer solution (pH 7.4 at 37°C) for 5 h. 相似文献
979.
Single‐layer graphene has received much attention because of its unique two‐dimensional crystal structure and properties. In this review, we focus on the graphene devices in solution, and their properties that are relevant to chemical and biological applications. We will discuss their charge transport, controlled by electrochemical gates, interfacial and quantum capacitance, charged impurities, and surface potential distribution. The sensitive dependence of graphene charge transport on the surrounding environment points to their potential applications as ultrasensitive chemical sensors and biosensors. The interfacial and quantum capacitance studies are directly relevant to the on‐going effort of creating graphene‐based ultracapacitors for energy storage. 相似文献
980.