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Deuterium Labeling (deuterium + labeling)
Selected AbstractsCollision-induced loss of AgH from Ag+ adducts of alkylamines, aminocarboxylic acids and alkyl benzyl ethers leads exclusively to thermodynamically favored product ionsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 2 2009Mathias Schäfer Abstract The loss of AgH from [M + Ag]+ precursor ions of tertiary amines, aminocarboxylic acids and aryl alkyl ethers is examined by deuterium labeling combined with collision activation (CA) dissociation experiments. It was possible to demonstrate that the AgH loss process is highly selective toward the hydride abstraction. For tertiary amines and aminocarboxylic acids, hydrogen originates from the ,-methylene group carrying the nitrogen function (formation of an immonium ion). In all cases examined, the most stable, i.e. the thermodynamically favored product ion is formed. In the AgH loss process, a large isotope effect operates discriminating against the loss of D. The [M + Ag]+ ion of benzyl methyl ether loses a hydride ion exclusively from the benzylic methylene group supporting the experimental finding that the AgH loss reaction selectively cleaves the weakest CH bond available. Copyright © 2008 John Wiley & Sons, Ltd. [source] Collision-induced dissociation of sulfur-containing imidazolium ionic liquidsJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 1 2008Alain Lesimple Abstract A number of 1,2-dimethylimidazole ionic liquids substituted on NII with alkyl chains of varying lengths terminated with sulfur-containing groups were investigated by electrospray high-resolution tandem Fourier-transform mass spectrometry. Fragmentation pathways are strongly dependent on the oxidation state of the sulfur and the alkyl chain length. The dissociations detected are rationalized by deuterium labeling, comparisons between homologous compounds and accurate mass data. Several homolytic processes are reported, leading to distonic ions and loss of hydrogen, methyl and other free radicals. Copyright © 2007 John Wiley & Sons, Ltd. [source] Gas-phase tautomers of protonated 1-methylcytosine.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2005Preparation, dissociation mechanisms, energetics Abstract Tautomers of 1-methylcytosine that are protonated at N-3 (1+) and C-5 (2+) have been specifically synthesized in the gas phase and characterized by tandem mass spectrometry and quantum chemical calculations. Ion 1+ is the most stable tautomer in aqueous and methanol solution and is likely to be formed by electrospray ionization of 1-methylcytosine and transferred in the gas phase. Gas-phase protonation of 1-methylcytosine produces a mixture of 1+ and the O-2-protonated tautomer (3+), which are nearly isoenergetic. Dissociative ionization of 6-ethyl-5,6-dihydro-1-methylcytosine selectively forms isomer 2+. Upon collisional activation, ions 1+ and 3+ dissociate by loss of ammonia and [C,H,N,O], whose mechanisms have been established by deuterium labeling and ab initio calculations. The main dissociations of 2+ following collisional activation are losses of CH2CNH and HNCO. The mechanisms of these dissociations have been elucidated by deuterium labeling and theoretical calculations. Copyright © 2005 John Wiley & Sons, Ltd. [source] Fragmentation study of diastereoisomeric 2-methyltetrols, oxidation products of isoprene, as their trimethylsilyl ethers, using gas chromatography/ion trap mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2004Wu Wang The diastereoisomeric 2-methyltetrols, 2-methylthreitol and 2-methylerythritol, were recently reported as major secondary aerosol components in natural forest aerosols and proposed as molecular markers for the photooxidation of isoprene. In this study, we examine the complex electron and methane chemical ionization behaviors of their trimethylsilyl ethers. In order to gain insight into their fragmentation behaviors, threitol and erythritol were studied as model compounds, and deuterium labeling of the trimethylsilyl groups and ion trap MS2 experiments were performed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Rearrangement with formamide extrusion in the electrospray mass spectra of aminoacylbenzylaminesRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 16 2001Jing Chen Several aminoacylbenzylamines and their analogs were synthesized and analyzed by electrospray ionization mass spectrometry together with high-resolution and tandem mass spectrometric techniques. Fragment ions ([M,+,H,,,CH3NO]+) were observed and attributed to a transfer of the benzyl group to the N-terminal amino group, leading to elimination of formamide. The proposed mechanism is supported by accurate mass measurements, and by experiments on deuterium labeling and variations of functional groups. Copyright © 2001 John Wiley & Sons, Ltd. [source] Stereo- and Biochemical Profiles of the 5-6- and 6-6-Junction Isomers of , - D -Mannopyranosyl [60]FullerenesCHEMISTRY & BIODIVERSITY, Issue 10 2004Yoshihiro Nishida The 5-6- and 6-6-junction isomers of , - D -mannopyranosyl [60]fullerene were studied by means of circular dichroism (CD), deuterium labeling, 1H-NMR, molecular-dynamics (MD) calculations, and a lectin-binding assay. The CD spectra of the O -acetylated derivatives allowed clear discrimination of the isomers, while the 1H-NMR spectra, with assistance from deuterium labeling and MD calculations, served to disclose the unique conformation and molecular geometry of each acetylated isomer in chloroform solution. The deprotected 5-6- and 6-6-isomers, which gave colloidal suspensions in aqueous mixtures, displayed marked activity in blocking lectin-induced hemagglutination by concanavalin,A. [source] | ||||||||||