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排序方式： 共有747条查询结果，搜索用时 15 毫秒
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In a previous work we have introduced an intramolecular induction correction model. In this work we have used the model to calculate the total dipol moment of six molecules as a function of two or three dihedral angles that are simultaneously varied in the molecules. It is found that the induction model behaves very well for the systems studied when compared with a regular force field model where fixed charges and dipoles are rotated along with the atoms of the molecules. This suggests that the proposed induction correction model can be used to model systems containing several dihedral angles around which rotations are performed. 相似文献
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Dube H Kasumaj B Calle C Saito M Jeschke G Diederich F 《Angewandte Chemie (International ed. in English)》2008,47(14):2600-2603
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Esther CR Jasin HM Collins LB Swenberg JA Boysen G 《Rapid communications in mass spectrometry : RCM》2008,22(5):701-705
Exhaled breath condensate (EBC) collection is a simple and non-invasive method to sample airway secretions, but analysis is limited by extensive and variable dilution of airway secretions within the condensate. To overcome this limitation, we developed a sensitive and specific liquid chromatography/tandem mass spectrometry (LC/MS/MS) method to simultaneously detect adenyl purines as biomarkers of inflammation and urea as a dilution marker in EBC. Separation prior to mass spectrometry was achieved using a C18 column with methanol and formic acid as the mobile phase, and characteristic precursor to product ion transitions of m/z 268 to 136 (for adenosine), m/z 348 to 136 (for AMP), and m/z 61 to 44 (for urea) were monitored for quantification. To correct for matrix effects, isotopically labeled adenosine, AMP, and urea were used as internal standards. Using these methods, we detected urea and the adenyl purines adenosine and AMP in EBC from seven subjects with cystic fibrosis (CF) and seven healthy controls and found that the AMP/urea ratio was elevated in the CF samples. These results demonstrate that mass spectrometry can be used successfully in EBC analysis to simultaneously detect a biomarker for airway inflammation and control for variable dilution. 相似文献
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Gunnar Jeschke Wilfried Hoffbauer Martin Jansen 《Chemistry (Weinheim an der Bergstrasse, Germany)》1998,4(9):1755-1761
Unexpected splittings in solid-state MAS-NMR spectra can indicate high rather than low local symmetry. A quantitative analysis of the resulting lineshapes provides information about geometry from a different range of space and time averaging than that of X-ray crystallography, as is demonstrated here for tetraphosphorus decaoxide (spectra on the right). 相似文献
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