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1H nuclear magnetic resonance relaxation investigation of huperzine E binding to acetylcholinesterase
DU Weihong, LI Yiming, JIANG Shanhao, TAN Changheng, ZHU Dayuan, GAN Qiuling
Front. Chem. China. 2007, 2 (4): 337-342.
https://doi.org/10.1007/s11458-007-0064-y
In order to search for better acetylcholinesterase (AchE) inhibitors, the binding properties of AchE with huperizine E, which is a derivative of huperzine A, were investigated with 1H nuclear magnetic resonance (1H NMR) method. The nonselective, selective and double-selective spin-lattice relaxation rates of some protons in huperzine E were acquired in the absence and presence of AchE at a concentration ratio of [ligand]/[protein] = 1 : 0.005. The enhancements of selective relaxation rates of these protons were obvious after adding AchE. The molecular motional correlation times of two pairs of protons, H-1a/H-1b and H-2/H-3, in the bound state at T = 298 K were 11.7 and 9.46 ns respectively, while they were 27.7 and 35.2 ps in the free state. All of these show that huperzine E has high binding affinity with AchE.
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Studies on confined crystallization behavior of polycaprolactone thin films
QIAO Congde, JI Xiangling, AN Lijia, JIANG Bingzheng, JIANG Shichun
Front. Chem. China. 2007, 2 (4): 343-348.
https://doi.org/10.1007/s11458-007-0065-x
The confined crystallization behavior of polycaprolactone (PCL) in thin and ultrathin films was studied by AFM (atomic force microscopy). It was found that the crystalline morphology of PCL depended on the film’s thickness. When the thickness is d>2 Rg (radius of gyration), the polymer can crystallize into spherulites; when Rg<d<2 Rg, a dense-branch morphology and dendrites could be found; when d<Rg, an islands structure could be obtained. Moreover, the effects of the crystallization temperature and the substrate and the molecular weight on the crystalline morphology were discussed. It was shown that the crystallization of PCL in thin films is a diffusion-controlled process, and it can be explained by diffusion-limited aggregation.
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In vitro investigation on cinnabar dissolution
ZENG Kewu, YANG Xiaoda, WANG Kui, WANG Qi
Front. Chem. China. 2007, 2 (4): 349-353.
https://doi.org/10.1007/s11458-007-0066-9
To study the effects of different chemical factors in the gastrointestinal tract, i.e. pH, proteins, amino acids, ionic strength and Na2S, on the dissolution of cinnabar. The content of the total mercury in various dissolutions of cinnabar was analyzed by UV/VIS Spectrophotometer. Laser Particle Size Analyzer measured the particle distributions in the dissolution of cinnabar. The chemical species of dissolved substance of cinnabar in the presence of Na2S were determined using ESI-MS. The results indicate that the solubility of cinnabar could be increased significantly in the presence of Na2S/S0, and strong acidic pH, respectively. While the influence of thiol amino acid on promoting dissolution remains relatively low. Cinnabar did not dissolve in the form of nanoparticle. It is postulated that cinnabar could be dissolved in the gastrointestinal tract in various forms of sulfur-containing mercury complexes.
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Preparation and characterization of ZrWMoO8 powders with different morphologies
LIU Qinqin, YANG Juan, SUN Xiujuan, CHENG Xiaonong
Front. Chem. China. 2007, 2 (4): 359-363.
https://doi.org/10.1007/s11458-007-0068-7
ZrWMoO8 powders with different morphologies were obtained using ammonium tungstate, molybdate tungstate and zirconium tungstate as the starting materials by dehydrating the precursor ZrWMoO7(OH)2(H2O)2. The precursor was studied by thermo-gravimetric and differential scanning calorimetry (TG-DSC). The influence of the gelling agents (HCl, HClO4, HNO3, H2SO4 and H3PO4) on the crystallization process and crystal morphology of the products prepared was investigated by X-ray powder diffraction (XRD), scanning electron micrograph (SEM) and X-ray fluorescence spectrometer (XRF). Results showed that the morphology of the ZrWMoO8 particles can be simply adjusted by changing the gelling agents, and the thermal expansion coefficients of cubic ZrWMoO8 prepared in HCl solution are -3.84×10-6 K-1 from 100! to 700!.
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Photocatalytic degradation of methylene blue on Fe3+-doped TiO2 nanoparticles under visible light irradiation
SU Bitao, WANG Ke, BAI Jie, MU Hongmei, TONG Yongchun, MIN Shixiong, SHE Shixiong, LEI Ziqiang
Front. Chem. China. 2007, 2 (4): 364-368.
https://doi.org/10.1007/s11458-007-0069-6
Fe3+-doped TiO2 composite nanoparticles with different doping amounts were successfully synthesized using sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and ultraviolet-visible spectroscopy (UV-Vis) diffuse reflectance spectra (DRS). The photocatalytic degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of Fe3+/TiO2 nanoparticles under visible light irradiation. The influence of doping amount of Fe3+ (ω: 0.00%–3.00%) on photocatalytic activities of TiO2 was investigated. Results show that the size of Fe3+/TiO2 particles decreases with the increase of the amount of Fe3+ and their absorption spectra are broaden and absorption intensities are also increased. Doping Fe3+ can control the conversion of TiO2 from anatase to rutile. The doping amount of Fe3+ remarkably affects the activity of the catalyst, and the optimum efficiency occurs at about the doping amount of 0.3%. The appropriate doping of Fe3+ can markedly increase the catalytic activity of TiO2 under visible light irradiation.
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Rapid functionalization of carbon nanotube and its electrocatalysis
DU Pan, SHI Yanmao, WU Ping, ZHOU Yaoming, CAI Chenxin
Front. Chem. China. 2007, 2 (4): 369-377.
https://doi.org/10.1007/s11458-007-0070-0
It was reported that carbon nanotube (CNT) was functionalized with the electroactive Nile blue (NB), which is a phenoxazine dye, by a method of adsorption to form a NB-CNT nanocomposite. The NB-CNT nanocomposite was characterized by several spectroscopic techniques, for example, Ultraviolet-visible spectroscopy (UV-VIS), Fourier transform infrared (FTIR), Raman spectroscopy and scanning electron microscopy (SEM) etc., and the results showed that NB could rapidly and effectively be adsorbed on the surface of CNT with a high stability without changing the native structure of NB and the structure properties of CNT. Moreover, it was shown that the dispersion ability of CNT in aqueous solution had a significantly improvement after CNT functionalized with NB even at a level of high concentration, for example, 5 mg of NB-CNT per 1 mL of H2O. The NB-CNT/ glasssy carbon (GC) electrode was fabricated by modifying NB-CNT nanocomposite on the GC electrode surface and its electrochemical properties were investigated by cyclic voltammetry. The cyclic voltammetric results indicate that CNT can improve the electrochemical behavior of NB and greatly enhance its redox peak currents. While the NB-CNT/GC electrode exhibited a pair of well-defined and nearly symmetrical redox peaks with the formal potential of (–0.422±0.002) V (versus SCE, 0.1 mol/L PBS, pH 7.0), which was almost independent on the scan rates, for electrochemical reaction of NB monomer; and the redox peak potential of NB polymer located at about –0.191 V. The experimental results also demonstrated that NB and CNT could synergistically catalyze the electrochemically oxidation of NADH (β-nicotinamide adenine dinucleotide, reduced form) and NB-CNT exhibited a high performance with lowing the overpotential of more than 560 mV. The NB-CNT/GC electrode could effectively sense the concentration of NADH, which was produced during the process of oxidation of substrate (e.g. ethanol) catalyzed by dehydrogenase (e.g. alcohol dehydrogenase). The presented method for functionalization of CNT had several advantages, such as rapid and facile CNT functionalization, easy electrode fabrication and high electrocatalytic activity, etc., and could be used for fabrication electrochemical biosensor on the basis of dehydrogenase.
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Studies on synthesis and molecular dynamics simulation of dendrimers containing amino acids and peptides
HE Gu, GUO Li, WANG Qianqian, MA Lifang, HE Zechao
Front. Chem. China. 2007, 2 (4): 378-382.
https://doi.org/10.1007/s11458-007-0071-z
A series of poly(ether-amide) dendrimers with amino acids and peptides as the peripheral functional groups was synthesized, and their structures were confirmed by nuclear magnetic resonance (NMR) and electrospray ionization-mass spectrometry (ESI-MS) spectrometry. Molecular dynamics simulation of the peptide dendrimers in solution was performed, indicating that, the prior conformations of the dendrimers were atom number dependent, i.e., with the increases of the atom number, the prior conformations were more spherical. Also, the amino acid α-C atom radial distribution indicated that, with larger peripheral groups, more back-folding of the dendrimers occurred.
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Photovoltaic devices from CdSe nanocrystals and conjugated polymer composites
LIU Yanshan, WANG Li, CAO Yong
Front. Chem. China. 2007, 2 (4): 383-386.
https://doi.org/10.1007/s11458-007-0072-x
The preparation of CdSe nanospheres (ns-CdSe) and their application as electron acceptor in conjugated polymer photovoltaic devices are reported. ns-CdSe with diameters of 5 nm were prepared through an organometallic method. The transmission electron microscopy (TEM), ultraviolet-visible (UV-Vis) absorption and photoluminescence (PL) spectra indicate that the CdSe nanocrystals (NCs) are monodispersed nanospheres with the first exciton absorption peak at around 625 nm and the emission peak at around 652 nm. The PL spectra of the ns-CdSe/polymer composite films show that the PL of the conjugated polymers is effectively quenched upon the addition of ns-CdSe. Photovoltaic devices were fabricated from the composites of ns-CdSe and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) or poly(3-hexylthiophene) (P3HT). Under AM1.5 illumination (100 mW/cm2), the short circuit current (ISC), open circuit voltage (VOC), fill factor (FF) and energy conversion efficiency (η) reached 1.56 mA/cm2, 0.75 V, 34.5% and 0.40%, respectively for device from the ns-CdSe/MEH-PPV (15 : 1 by weight) and 1.93 mA/cm2, 0.65 V, 38.4% and 0.48%, respectively for device from the ns-CdSe/P3HT (10 : 1 by weight).
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Preparation and characterization of Cr2O3 system optically variable pigment
DU Haiyan, ZHANG Hua, CHEN Qirong, SUN Jiayue, XU Wencai, MA Erjun
Front. Chem. China. 2007, 2 (4): 398-402.
https://doi.org/10.1007/s11458-007-0075-8
An optically variable pigment was produced by wet chemical method, where TiO2-coated mica with interference colors acted as the substrate materials. The structure of the pigment was characterized by X-ray diffraction (XRD), and its optically variable effect was investigated by X-Rite MA86 II five angles spectrophotometer. The impact of different interference substrate materials for improving the color travel effect was studied, and the influence of white and black background on the hue and the color travel effect were studied. Results showed that optically variable pigments can be prepared by coating Cr2O3 on the surface of the pretreated TiO2-coated mica. The color travel effect was sensitive to the change of substrate materials, and different backgrounds can influence the hue and the color travel effect of the pigment.
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Studies on high chemical reactivity of nano-NaH
FAN Yinheng, JIN Dan, WU Qiang, LIU Tong, ZOU Yunling, XU Jie
Front. Chem. China. 2007, 2 (4): 403-406.
https://doi.org/10.1007/s11458-007-0076-7
A comparison between the initial reaction rates of nanometric and commercial NaH has been studied in four test reactions: 1) hydrogenolysis of chlorobenzene; 2) selective reduction of cinnamaldehyde to cinnamyl alcohol; 3) metallation of dimethyl sulfoxide; and 4) catalytic hydrogenation of olefins. The experimental results indicate that when NaH is used as a chemical reagent in the first three reactions, the initial reaction rates of nano-NaH is 230, 120 and 110 times higher than those of the commercial ones respectively, and it is in agreement with the difference in specific surface areas between these two forms of NaH. When NaH is used as a catalyst component together with Cp2TiCl2 in the fourth reaction, catalyst with nano-NaH gives extremely high activity in the hydrogenation of olefins, while the one with commercial NaH gives no activity at all even if a large amount of the commercial NaH is used to make the total surface area equivalent to that of nano-NaH. Thus, it is evident that although large specific surface area is important for nano-NaH to be used as a catalyst component, high surface energy with surface defects seems to be more important. The large specific surface and the activated surface of nano-NaH with high surface energy should be the main factors for their extremely high chemical reactivity, while whether the former or the latter one plays a leading role depends on the type of reactions involved.
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Synthesis and photoluminescence properties of 8-hydroxyquinoline derivatives and their metallic complexes
OUYANG Xinhua, ZENG Heping, XIE Yan
Front. Chem. China. 2007, 2 (4): 407-413.
https://doi.org/10.1007/s11458-007-0077-6
Three new 8-hydroxyquinoline derivatives, i.e. 5-[(4-styryl-benzylidene)-amino]-quinolin-8-ol (1), 5-[(4-bromo-2-fluoro-benzylidene)-amino]-quinoline-8-ol (2) and 2-[2-(9-ethyl-9H-carbazol-2yl)-vinyl]-quinolin-8-ol (3), and their metallic complexes were synthesized and identified by ultraviolet-visible (UV-Vis), 1H nuclear magnetic resonance (1H NMR), Fourier transform infrared spectrometer (FTIR), mass spectrometry (MS) spectra and elemental analyses. Their fluorescence properties were studied by photoluminescence, which indicated that the luminescence wavelength of 5- and 2-substitued-8-hydroxyquinoline derivatives shifted to red in comparison with that of 8-hydroxyquinoline. Meanwhile, the fluorescence lifetime of 2-[2-(9-ethyl-9H-carbazol-2yl)-vinyl]-quinolin-8-ol and its zinc complex showed long lifetime in benzene solution.
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Different protein expression of myocardium from Chinese mini-swine model of myocardial infarct
ZHAO Yanfeng, YE Nengsheng, ZHANG Rongli, FENG Xue, LUO Guoan, WANG Yiming
Front. Chem. China. 2007, 2 (4): 422-427.
https://doi.org/10.1007/s11458-007-0080-y
High-resolution two-dimensional gel electrophoresis (2-DE), followed by computer-assisted image analysis was used to screen protein patterns of normal and infarcted myocardial tissues for quantitative and qualitative differences in protein expression. In the gels of pH 5–8 immobilized pH gradient (IPG) strips, 851 protein spots were detected in normal myocardial tissue and 1 032 protein spots were resolved in infarcted myocardial tissue. Thirteen protein spots only expressed in normal myocardial tissue, and 14 protein spots only expressed in infarcted myocardial tissue. Results also showed that 49 protein spots displayed quantitative changes in expression between normal and infarcted myocardial tissue. Eleven protein spots were subjected to mass spectrometry (MS) analysis and seven proteins were identified by peptide mass fingerprinting (PMF). These proteins may be involved in cardiovascular injury, and could play an important role in the treatment of coronary heart disease.
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Synthesis of 3,6-bisubstituted phenyl-bi-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives
QIAN Jianhua, LIU Lin, WANG Daolin, XING Jinjuan
Front. Chem. China. 2007, 2 (4): 428-430.
https://doi.org/10.1007/s11458-007-0081-x
2,5-Bihydrazino-1,3,4-thiadiazole (2) was synthesized by condensation of 2,5-bimercapto-1,3,4-thiadiazole (1) with hydrazine hydrate, and compound 2 reacted with acyl chloride to give 2,5-biacylhydrazino-1,3,4-thiadiazole derivatives (3a?3e). Ring closure of compounds 3a?3e was achieved with POCl3 as the cyclization agent giving 3,6-bisubstituted phenyl-bi-1,2,4-triazolo[3,4-b]-1,3,4-thiadiazole derivatives (4a?4e), respectively. The novel compounds were identified by elemental analysis, and by infrared (IR), 1H- nuclear magnetic resonance (NMR), and mass (MS) spectrometry. The mechanism of the cyclization is also discussed.
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Preparation and properties of luminous materials of CaSiO3 : Pb, Mn by sol-gel method
YANG Liangzhun, FANG Min, Liu Yuejiao, LIU Chao, WANG Xiuying, YU Xibin
Front. Chem. China. 2007, 2 (4): 442-446.
https://doi.org/10.1007/s11458-007-0084-7
The luminous materials of CaSiO3 : Pb, Mn were synthesized by sol-gel method and ultrasound technology. The properties of the phosphors were characterized by luminescence spectrum, differential thermal analysis and thermal gravimetry analysis (DTA-TG), X-ray diffraction (XRD), Fourier transform infrared spectrometer (FT-IR) and transmission electron microscopy (TEM). The effects of factors such as the synthetic material compositions, ultrasound time and annealed temperature on phosphorescent brightness of sample were studied and the optimum synthetic conditions were determined. The results show that, compared with the sample made by the high temperature solid-state reaction, the luminescent intensity of the CaSiO3 : Pb, Mn sample increased by about 200% and the mean diameter of particles of the sample decreased by about 300 nm.
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