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利用快原子轰击质谱(FABMS)及解吸电子轰击质谱(DEIMS)方法,分析了电场辐照前后的5种中药有效成分,证明电场辐照灭菌并不改变其化学结构,讨论了底物效应及正,负快原子轰击质谱的差异,以及与电吸电子轰击质谱的不同断裂规律,同时利用B/E联动扫描(亚稳离子测定)进行了验证。 相似文献
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应用激光解吸质谱和十二烷基硫酸钠—聚丙烯酰胺凝胶电泳分析蛇毒?… 总被引:1,自引:0,他引:1
应用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)和SDS-聚丙烯酰胺凝胶电流对吉林省两地市的同种白眉蝮蛇蛇毒中具有抗栓塞药效的精氨酸酯酶进行了分析了分析和比较。MALDI-TOF-MS法具有快速、准确度高、灵敏度高的优点,两种方法结合,互为补充,取得了令人满意的结果。MALDI-TOF-MS完全可以直接用作蛇毒成分分离过程中重要的研究手段。 相似文献
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本文报道了一系列含锗有机酸在甘油中的快原子轰击质谱(FABMS)及共在间硝基苄醇(NBA)中的正、负离子FABMS。这些含锗有机酸在不同的底物中的FABMS显示了不同的特征。负离子谱提供了分子量信息,正、负离子谱可为这类化合物的结构鉴定提供互相补充的信息。讨论了底物和取代基对FABMS的影响,正、负离子的产生机制及离子的亚稳分解途径。 相似文献
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采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF-MS)对杯芳烃化合物进行了分析。探讨了样品的制备条件、仪器操作参数等因素对测定结果的影响。25种样品的质谱数据表明,利用MALDI-TOF-MS可非常方便地得到灵敏度、分辨率、准确度均较高,且易于识别和解析的质谱图,为此类化合物的质谱表征提供和建立了一种新的高效分析方法。 相似文献
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I. Brissaud J. X. Wang P. Chevallier 《Journal of Radioanalytical and Nuclear Chemistry》1989,131(2):399-413
Advantages of X-ray fluorescence with the use of Synchrotron Radiation are emphasized (intensity, polarization, tunability of energy). The experimental set-up and the fast computer system for the data reduction without standards are presented. The results are in good agreement with standard references. Examples of applications are presented: old coins and potteries were studied in archaeological domain; metal alloys were analyzed; element composition of bulk samples of volcanic rocks, sublimates and aerosols were determined. 相似文献
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石墨炉原子吸收光谱无标样分析法的研究:Ⅳ.实际样品的分析 总被引:1,自引:0,他引:1
以有机基体改进剂、管壁原子化、热解涂层石墨管、峰面积积分吸收信号、D2灯或Zeeman效应扣除背景,有效地控制和消除了海水基体对Cd,Co,Cr,CuMn,NiPb等元素的干扰。在此前提下,用GFAAS无标样分析汉分析了实验海水样品中的痕量元素,与极谱法及间接火焰原子吸收法测得的结果相符,测得质控海水样品的结果与标准值亦很吻合,而且检出限和回收率都达达到要求。 相似文献
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The structures and stability of triplet HFSiS system were investigated by density functional theory(DFT)in detail. The optimized geometrical parameters and vibrational frequencies of all species were obtained at the level of B3LYP/6-311G** and the assignments of them were performed. At the same theoretical level, IRC calculations were carried. In addition, the singlet-point energies and relative energies were calculated by high level electron-correlation CCSD(T)/6-311G**. The isomerized and dissociated processes were explained by vibrational mode analysis method. The triplet PES is compared to the singlet one. The results are as the following: there are six isomers on the triplet PES. Moreover, 3HFSiS is found to be the most thermodynamically and kinetically stable and is able to be observed in experiments. Structures 2 are the more stable ones between the two group bond cycled isomers and are predicted to be detected. 3SiSHF is the most unstable isomer in thermodynamics and kinetics. 相似文献
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Legenski N Zhou C Zhang Q Han B Wu J Chen L Cheng H Forrey RC 《Journal of computational chemistry》2011,32(8):1711-1720
Atomic force fields for simulating copper, silver, and gold clusters and nanoparticles are developed. Potential energy functions are obtained for both monatomic and binary metallic systems using an embedded atom method. Many cluster configurations of varying size and shape are used to constrain the parametrization for each system. Binding energies for these training clusters were computed using density functional theory (DFT) with the Perdew-Wang exchange-correlation functional in the generalized gradients approximation. Extensive testing shows that the many-body potentials are able to reproduce the DFT energies for most of the structures that were included in the training set. The force fields were used to calculate surface energies, bulk structures, and thermodynamic properties. The results are in good agreement with the DFT values and consistent with the available experimental data. 相似文献
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总结分析了87例逆行胰胆管造影检查失败原因,其中解剖走形异常、溃疡及炎性狭窄或出血、食道静脉曲线失败25例;乳头位位置异常、乳头充血、肿胀或增生样改变及十二指肠憩室缘内乳头而失败45例;毕氏Ⅱ式术后胃检查失败2例;护理因素、病人不合作或不能忍受失败5例。结合有关文献,探讨了逆行胰胆管造影检查术失败的原因及提高成功率的方法及注意事项,以提高检查成功率。 相似文献
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Dey A Kirchner MT Vangala VR Desiraju GR Mondal R Howard JA 《Journal of the American Chemical Society》2005,127(30):10545-10559
The supramolecular synthon approach to crystal structure prediction (CSP) takes into account the complexities inherent in crystallization. The synthon is a kinetically favored unit, and through analysis of commonly occurring synthons in a group of related compounds, kinetic factors are implicitly invoked. The working assumption is that while the experimental structure need not be at the global minimum, it will appear somewhere in a list of computationally generated structures so that it can be suitably identified and ranked upward using synthon information. These ideas are illustrated with a set of aminophenols, or aminols. In the first stage, a training database is created of the 10 isomeric methylaminophenols. The crystal structures of these compounds were determined. The prototypes 2-, 3-, and 4-aminophenols were also included in the training database. Small and large synthons in these 13 crystal structures were then identified. Small synthons are of high topological but low geometrical value and are used in negative screens to eliminate computationally derived structures that are chemically unreasonable. Large synthons are more restrictive geometrically and are used in positive screens ranking upward predicted structures that contain these more well-defined patterns. In the second stage, these screens are applied to CSP of nine new aminols carried out in 14 space groups. In each space group, up to 10 lowest energy structures were analyzed with respect to their synthon content. The results are encouraging, and the predictions were classified as good, unclear, or bad. Two predictions were verified with actual crystal structure determinations. 相似文献
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M. Anastasiou Th. Hasapis T. Zorba E. Pavlidou K. Chrissafis K. M. Paraskevopoulos 《Journal of Thermal Analysis and Calorimetry》2006,84(1):27-32
Historic
plasters from wall paintings of Byzantine and post-Byzantine churches situated
in the Balkan region were studied. All wall paintings were made with fresco
technique and are dated from IX - XVI century. Plaster samples were followed
from room temperature to 1000°C by Thermogravimetric (TG) and Differential
Thermal Analysis (DTA), and one or two significant temperature regions, corresponding
to thermal decomposition mechanisms were observed. The analysis of the plaster
samples and the composition characterization was carried out using also, Fourier
Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM).
Although the main components are calcite and quartz (from sand) in different
proportions, there are differences between them such as the presence of gypsum
being either as a constituent element or due to environmental pollution. The
results are examined comparatively taking into account the creation time and
place of the paintings. 相似文献
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C–H?N and C–H?S hydrogen bonds were analyzed in complexes where acetylene, ethylene, methane and their derivatives are proton donors while ammonia and hydrogen sulfide are proton acceptors. Ab initio calculations were performed to analyze those interactions; MP2 method was applied and the following basis sets were used: 6-311++G(d,p), aug-cc-pVDZ and aug-cc-pVTZ. The results showed that hydrogen bonds for complexes with ammonia are systematically stronger than such interactions in complexes with hydrogen sulfide. If the fluorine substituted hydrocarbons are considered then F-substituents enhance the strength of hydrogen bonding. For a few complexes, mainly those where carbon atom in proton donating C–H bond possesses sp3 hybridization, the blue-shifting hydrogen bonds were detected. Additionally, Quantum Theory of ‘Atoms in Molecules’ and Natural Bond Orbitals method were applied to analyze H-bond interactions. 相似文献