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Peter Max Gehrig Bernd Roschitzki Dorothea Rutishauser Sonja Reiland Ralph Schlapbach 《Rapid communications in mass spectrometry : RCM》2009,23(10):1435-1445
In order to investigate gas‐phase fragmentation reactions of phosphorylated peptide ions, matrix‐assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) tandem mass (MS/MS) spectra were recorded from synthetic phosphopeptides and from phosphopeptides isolated from natural sources. MALDI‐TOF/TOF (TOF: time‐of‐flight) spectra of synthetic arginine‐containing phosphopeptides revealed a significant increase of y ions resulting from bond cleavages on the C‐terminal side of phosphothreonine or phosphoserine. The same effect was found in ESI‐MS/MS spectra recorded from the singly charged but not from the doubly charged ions of these phosphopeptides. ESI‐MS/MS spectra of doubly charged phosphopeptides containing two arginine residues support the following general fragmentation rule: Increased amide bond cleavage on the C‐terminal side of phosphorylated serines or threonines mainly occurs in peptide ions which do not contain mobile protons. In MALDI‐TOF/TOF spectra of phosphopeptides displaying N‐terminal fragment ions, abundant b–H3PO4 ions resulting from the enhanced dissociation of the pSer/pThr–X bond were detected (X denotes amino acids). Cleavages at phosphoamino acids were found to be particularly predominant in spectra of phosphopeptides containing pSer/pThr–Pro bonds. A quantitative evaluation of a larger set of MALDI‐TOF/TOF spectra recorded from phosphopeptides indicated that phosphoserine residues in arginine‐containing peptides increase the signal intensities of the respective y ions by almost a factor of 3. A less pronounced cleavage‐enhancing effect was observed in some lysine‐containing phosphopeptides without arginine. The proposed peptide fragmentation pathways involve a nucleophilic attack by phosphate oxygen on the carbon center of the peptide backbone amide, which eventually leads to cleavage of the amide bond. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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Dorothea Bahns 《Annales Henri Poincare》2010,11(7):1273-1283
It is shown that the n-point functions of scalar massive free fields on the noncommutative Minkowski space are distributions which are boundary
values of analytic functions. Contrary to what one might expect, this construction does not provide a connection to the popular
traditional Euclidean approach to noncommutative field theory (unless the time variable is assumed to commute). Instead, one
finds Schwinger functions with twistings involving only momenta that are on the mass-shell. This explains why renormalization
in the traditional Euclidean noncommutative framework crudely differs from renormalization in the Minkowskian regime. 相似文献
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Inventiones mathematicae - 相似文献
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Carsten Bolm Konrad Weickhardt Margareta Zehnder Dorothea Glasmacher 《Helvetica chimica acta》1991,74(4):717-726
The synthesis of the complexes 3 of various metals ligated to chiral 4,5-dihydro-2-(2′-oxidophenyl-?O)oxazoles-?N is described (Scheme). Three of them, i.e. 3a , 3e , and 3f containing CuII, ZnII and NiII, respectively, were analyzed by X-ray diffraction studies. A series of CuII complexes ( 6a – d ) with differently substituted dihydrooxazoles have been synthesized. 相似文献
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Franziska Preusse Elke van der Meer Dorothea Ullwer Martin Brucks Frank Krueger Isabell Wartenburger 《ZDM》2010,42(6):635-647
Intelligence is known to predict scholastic achievement and enables high performance in cognitive tasks. Fluid intelligence is strongly related to analogical reasoning abilities, which are fundamental to mathematical thinking. Geometric analogical reasoning is a prototypical measure of fluid intelligence. However, the cerebral correlates of geometric analogical reasoning and their developmental modulation over time are still rarely investigated. We report a 1-year follow-up functional magnetic resonance imaging study of a geometric analogical reasoning task in high fluid intelligence high-school students. This study was designed to characterise the cerebral correlates of geometric analogical reasoning and to improve our knowledge about the impact of general cognitive development on behavioural performance and on cerebral mechanisms underlying geometric analogical reasoning in adolescents. Our data indicate that a fronto-parietal network comprising the left and right parietal lobes and the left middle frontal gyrus was equally modulated by task difficulty at both measuring time points. At the behavioural level, however, participants showed improvements in performance at the second measuring time point. The behavioural improvements point to a more efficient task processing. As this is not accompanied by differential recruitment of fronto-parietal brain regions, the data suggest an increase in neural efficiency for these brain regions. 相似文献