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81.
Characterization of polyphosphoesters by fourier transform ion cyclotron resonance mass spectrometry
Malgorzata A. Kaczorowska Helen J. Cooper 《Journal of the American Society for Mass Spectrometry》2009,20(12):2238-2247
FT-ICR mass spectrometry, together with collision-induced dissociation and electron capture dissociation, has been used to
characterize the polyphosphoester poly[1,4-bis(hydroxyethyl)terephthalate-alt-ethyloxyphosphate] and its degradation products. Three degradation pathways were elucidated: hydrolysis of the phosphate-[1,4-bis(hydroxyethyl)terephthalate]
bonds; hydrolysis of the phosphate-ethoxy bonds; and hydrolysis of the ethyl-terephthalate bonds. The dominant degradation
reactions were those that involved the phosphate groups. This work constitutes the first application of mass spectrometry
to the characterization of polyphosphoesters and demonstrates the suitability of high mass accuracy FT-ICR mass spectrometry,
with CID and ECD, for the structural analysis of polyphosphoesters and their degradation products. 相似文献
82.
Victor A. Mikhailov Helen J. Cooper 《Journal of the American Society for Mass Spectrometry》2009,20(5):763-771
Here, we show that to perform activated ion electron capture dissociation (AI-ECD) in a Fourier transform ion cyclotron resonance
(FT-ICR) mass spectrometer equipped with a CO2 laser, it is necessary to synchronize both infrared irradiation and electron capture dissociation with ion magnetron motion.
This requirement is essential for instruments in which the infrared laser is angled off-axis, such as the Thermo Finnigan
LTQ FT. Generally, the electron irradiation time required for proteins is much shorter (ms) than that required for peptides
(tens of ms), and the modulation of ECD, AI ECD, and infrared multiphoton dissociation (IRMPD) with ion magnetron motion is
more pronounced. We have optimized AI ECD for ubiquitin, cytochrome c, and myoglobin; however the results can be extended to other proteins. We demonstrate that pre-ECD and post-ECD activation
are physically different and display different kinetics. We also demonstrate how, by use of appropriate AI ECD time sequences
and normalization, the kinetics of protein gas-phase refolding can be deconvoluted from the diffusion of the ion cloud and
measured on the time scale longer than the period of ion magnetron motion. 相似文献
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Begin with a set of four points in the real plane in general position. Add to this collection the intersection of all lines
through pairs of these points. Iterate. Ismailescu and Radoičić (Comput. Geom. 27:257–267, 2004) showed that the limiting set is dense in the plane. We give doubly exponential upper and lower bounds on the number of points
at each stage. The proof employs a variant of the Szemerédi–Trotter Theorem and an analysis of the “minimum degree” of the
growing configuration. 相似文献
86.
Although much discussed, the original intent of Problem 10 of the Moscow Mathematical Papyrus continues to be an unresolved question. This essay proposes a possible solution to the issue by joining together aspects of two theories on the subject advanced in the 1930s by W. W. Struve and T. E. Peet. From this point of beginning it is shown that the problem’s “basket” may originally have been intended to be understood as being of a specific actual size, thus revealing a set of correlations and insights regarding early Middle Kingdom mathematical capabilities and grain measurement concerns. 相似文献
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Douglas J. Morrison Karen Cooper Tom Preston 《Rapid communications in mass spectrometry : RCM》2010,24(12):1799-1804
Carbon isotope analysis by bulk elemental analysis coupled with isotope ratio mass spectrometry has been the mainstay of δ13C analyses both at natural abundance and in tracer studies. More recently, compound‐specific isotope analysis (CSIA) has become established, whereby organic constituents are separated online by gas or liquid chromatography before oxidation and analysis of CO2 for constituent δ13C. Theoretically, there should be concordance between bulk δ13C measurements and carbon‐weighted δ13C measurements of carbon‐containing constituents. To test the concordance between the bulk and CSIA, fish oil was chosen because the majority of carbon in fish oil is in the triacylglycerol form and ~95% of this carbon is amenable to CSIA in the form of fatty acids. Bulk isotope analysis was carried out on aliquots of oil extracted from 55 fish samples and δ13C values were obtained. Free fatty acids (FFAs) were produced from the oil samples by saponification and derivatised to fatty acid methyl esters (FAMEs) for CSIA by gas chromatography/combustion/isotope ratio mass spectrometry. A known amount of an internal standard (C15:0 FAME) was added to allow analyte quantitation. This internal standard was also isotopically calibrated in both its FFA (δ13C = ?34.30‰) and FAME (δ13C = ?34.94‰) form. This allowed reporting of FFA δ13C from measured FAME δ13C values. The bulk δ13C was reconstructed from CSIA data based on each FFA δ13C and the relative amount of CO2 produced by each analyte. The measured bulk mean δ13C (SD) was ?23.75‰ (1.57‰) compared with the reconstructed bulk mean δ13C of ?23.76 (1.44‰) from CSIA and was not significantly different. Further analysis of the data by the Bland‐Altman method did not show particular bias in the data relative to the magnitude of the measurement. Good agreement between the methods was observed with the mean difference between methods (range) of 0.01‰ (?1.50 to 1.30). Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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