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981.
982.
983.
Controllable Release and High‐Efficiency Collection of Hydrogen Peroxide: Application on the Quantitative Investigation of Biomolecule Oxidation Induced by Reactive Oxygen Species 下载免费PDF全文
Hydrogen peroxide and hydroxyl radical, both important members of the reactive oxygen species (ROS) family, can cause serious oxidative damages in biological systems. In order to proclaim and prevent oxidation stress, researches on the biomolecule oxidation induced by H2O2 or OH. are in crucial need. However, due to the high reactivity of ROS, traditional methods are difficult to achieve the in situ quantitative investigations on those reactions involving ROS. In this work, using scanning electrochemical microscopy technique (SECM) in a tip generation‐substrate collection mode (TG‐SC), the controllable release and the high‐efficiency collection of electrogenerated H2O2 were achieved. Compared to ex situ fluorescence method, SECM improved the collection efficiency approximately two times larger. Based on it, SECM combined with surface plasmon resonance (SPR) was employed to in situ monitor the protein oxidation (taking Cu12+? MT as a model) induced by H2O2. OH., which was generated from the interaction between H2O2 and Cu12+? MT, can attack the peptide chain and induced the unrepairable protein oxidation damage. The whole process was quantitatively characterized by SPR, and the linear relationship between SPR dip shift and the amounts of released H2O2 was successfully built. Our work proves that the combined SECM‐SPR technique can realize the in situ quantitative determinations of the biomolecule oxidation induced by ROS, which affords an avenue for further elucidation on the mechanisms of oxidation stress in organisms. 相似文献
984.
Liang Wang Fuxing Xu Xinhua Dai Xiang Fang Chuan-Fan Ding 《Journal of the American Society for Mass Spectrometry》2014,25(4):548-555
A mesh-electrode linear ion trap (ME-LIT) mass analyzer was developed and its performance was primarily characterized. In conventional linear ion trap mass analyzers, the trapped ions are mass-selected and then ejected in a radial direction by a slot on a trap electrode. The presence of slots can strongly affect the electric field distribution in the ion trapping region and distort the mass analysis performance. To compensate for detrimental electric field effects, the slot is usually designed and fabricated to be as small as possible, and also has very high mechanical accuracy and symmetry. A ME-LIT with several mesh electrodes was built to compensate for the effects caused by slots. Each mesh electrode was fabricated from a plate electrode with a relatively large slot and the slot was covered with a conductive mesh. Our preliminary experimental results show that the ME-LIT could considerably diminish the detrimental electric field effects caused by slots, and increase the mass resolving power and ion detection efficiency. Even with 4-mm-wide slots, a mass resolution in excess of 600 was obtained using the ME-LIT. Mass resolution could be remarkably improved using mesh electrodes in ion traps with asymmetric electrodes. The stability diagram of the ME-LIT was mapped, and highly efficient tandem mass spectrometry was demonstrated. The ME-LIT was qualified as a LIT mass analyzer. The ME-LIT can improve the mass resolution and decrease the requirements of mechanical accuracy and symmetry of slots, so it shows potential for a wide range of practical uses. Figure
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985.
Hongmei Peng Bin Wang Jinggang Gai Jinyao Chen Feng Yang Ya Cao Huilin Li Jian Kang Ming Xiang 《先进技术聚合物》2014,25(12):1464-1470
Large amount of work has been published on the isotacticity–properties relationship of isotactic polypropylene (iPP). However, the stereo‐defect distribution dependence of morphology and mechanical properties of iPP injection molding samples is still not clear. In this study, two different isotactic polypropylene (iPP) resins (PP‐A and PP‐B) with similar average isotacticity but different stereo‐defect distribution were selected to investigate the morphology evolution and mechanical properties (tensile and notching) of their injection molding samples using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), 2D wide angle X‐ray diffraction (2D‐WAXD), and scanning electron microscope (SEM). The results of DMA showed that the molecular movement ability of PP‐A (with less uniform distribution of stereo‐defect) was stronger than that of PP‐B, meanwhile the analysis of DSC and SEM suggested that after injection molding, smaller spherullites, and crystals with higher perfection had formed in the specimens of PP‐A. The resulting of tensile properties of PP‐A were found to be better than that of PP‐B. The results of morphology evolution by SEM observation and 2D‐WAXD showed that PP‐A is more likely to occur interspherulite deformation and can disperse the tensile stress more efficiently, and therefore, its crystal structure can withstand a greater force when tensile stress is applied. On the other hand, PP‐B has larger spherulites and boundaries, and low perfection of lamellaes, and the intraspherulte deformation tend to take place. It is easier for the crystal of PP‐B to be broken up and reoriented along the tensile direction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
986.
Mei Xiang Qingjie Jiao Yanli Zhu Jinyang Yu Liping Chen 《Journal of Thermal Analysis and Calorimetry》2014,116(3):1159-1163
The thermal behavior of the energetic material 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaaza-tetracyclo-[5.5.0.05,9.03,11]-dodecane (HNIW or CL-20) and its mixtures with aluminum under linear temperature control condition and adiabatic condition were investigated by DSC-TG-MS-FT-IR and ARC. Two different particle sizes of aluminum powder (10 μm and 50 nm) were added into CL-20. The influence of particle size on the thermal behavior of CL-20 was studied by using of these apparatuses. The enthalpies of reaction and onset temperatures were determined for various heating rates. The kinetic parameters were found according to Kissinger method, Ozawa method, and Friedman method based on DSC data. The gaseous products from the decomposition of CL-20 and its mixtures were determined by simultaneous MS-FT-IR experiments. ARC measurements were performed to investigate the thermal stability of the samples. The onset temperature, adiabatic temperature rise, self-heat rate, time to maximum rate, and pressure–temperature profile were found from the data measured by ARC. Based on these results, the catalytic effect of aluminum powder was studied. 相似文献
987.
Yude Zhang Qinfu Liu Jingjing Xiang Shilong Zhang Ray L. Frost 《Journal of Thermal Analysis and Calorimetry》2014,117(3):1201-1210
A series of rubber composites were prepared by blending styrene-butadiene rubber (SBR) latex and the different particle sized kaolinites. The thermal stabilities of the rubber composites were characterized using thermogravimetry, digital photography, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy. Kaolinite SBR composites showed much greater thermal stability when compared with that of the pure SBR. With the increase of kaolinite particle size, the pyrolysis products became much looser; the char layer and crystalline carbon content gradually decreased in the pyrolysis residues. The pyrolysis residues of the SBR composites filled with the different particle sized kaolinites showed some remarkable changes in structural characteristics. The increase of kaolinite particle size was not beneficial to form the compact and stable crystalline carbon in the pyrolysis process, and resulted in a negative influence in improving the thermal stability of kaolinite/SBR composites. 相似文献
988.
Large Hexagonal Bi‐ and Trilayer Graphene Single Crystals with Varied Interlayer Rotations 下载免费PDF全文
Zheng Yan Yuanyue Liu Long Ju Zhiwei Peng Dr. Jian Lin Dr. Gunuk Wang Dr. Haiqing Zhou Changsheng Xiang E. L. G. Samuel Carter Kittrell Dr. Vasilii I. Artyukhov Prof. Feng Wang Prof. Boris I. Yakobson Prof. James M. Tour 《Angewandte Chemie (International ed. in English)》2014,53(6):1565-1569
Bi‐ and trilayer graphene have attracted intensive interest due to their rich electronic and optical properties, which are dependent on interlayer rotations. However, the synthesis of high‐quality large‐size bi‐ and trilayer graphene single crystals still remains a challenge. Here, the synthesis of 100 μm pyramid‐like hexagonal bi‐ and trilayer graphene single‐crystal domains on Cu foils using chemical vapor deposition is reported. The as‐produced graphene domains show almost exclusively either 0° or 30° interlayer rotations. Raman spectroscopy, transmission electron microscopy, and Fourier‐transformed infrared spectroscopy were used to demonstrate that bilayer graphene domains with 0° interlayer stacking angles were Bernal stacked. Based on first‐principle calculations, it is proposed that rotations originate from the graphene nucleation at the Cu step, which explains the origin of the interlayer rotations and agrees well with the experimental observations. 相似文献
989.
Highly Efficient Electrocatalysts for Oxygen Reduction Based on 2D Covalent Organic Polymers Complexed with Non‐precious Metals 下载免费PDF全文
Dr. Zhonghua Xiang Dr. Yuhua Xue Prof. Dapeng Cao Ling Huang Prof. Jian‐Feng Chen Prof. Liming Dai 《Angewandte Chemie (International ed. in English)》2014,53(9):2433-2437
A class of 2D covalent organic polymers (COPs) incorporating a metal (such as Fe, Co, Mn) with precisely controlled locations of nitrogen heteroatoms and holes were synthesized from various N‐containing metal–organic complexes (for example, metal–porphyrin complexes) by a nickel‐catalyzed Yamamoto reaction. Subsequent carbonization of the metal‐incorporated COPs led to the formation of COP‐derived graphene analogues, which acted as efficient electrocatalysts for oxygen reduction in both alkaline and acid media with a good stability and free from any methanol‐crossover/CO‐poisoning effects. 相似文献
990.
Yong‐Gang Zhang Xiang‐Lei Liu Zeng‐Yang He Xi‐Ming Li Hong‐Jian Kang Prof. Dr. Shi‐Kai Tian 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(10):2765-2769
An unprecedented oxidative arylation reaction of terminal alkenes with simple aroyl hydrazides has been developed under aerobic conditions for the stereoselective synthesis of 1,2‐disubstituted alkenes. A range of aroyl hydrazides underwent palladium/copper‐catalyzed oxidative Mizoroki–Heck reaction with terminal alkenes open to air in a 1:1 mixture of dimethyl sulfoxide and acetonitrile to give structurally diverse 1,2‐disubstituted alkenes in moderate to excellent yields with excellent regio‐ and E‐selectivity. The reaction tolerated a wide variety of functional groups, such as alkoxy, hydroxy, amino, fluoro, chloro, bromo, cyano, nitro, ester, amide, imide, phosphine oxide, and sulfone groups, and, moreover, molecular oxygen and dimethyl sulfoxide were demonstrated to serve as terminal oxidants. This study provides a useful method for the stereoselective synthesis of 1,2‐disubstituted alkenes through direct transformation of the vinylic C?H bonds in terminal alkenes. 相似文献