Production and Characterization of Beams of Polystyrene Ions

1986 ◽  
Vol 39 (9) ◽  
pp. 1421 ◽  
Author(s):  
AG Craig ◽  
PJ Derrick
Keyword(s):  
Gas Phase ◽  
Bond Cleavage ◽  
Molecular Ions ◽  
Emitter Temperature ◽  
Charge Delocalization ◽  
Mass Fragment ◽  
Fragment Ions ◽  
Efficient Charge ◽  
Low Mass

The formation of gaseous polystyrene molecular ions [M]+ by means of the technique of field desorption is proposed to involve creation of a charged sample/gas interface and subsequent field evaporation of ions. The molecular ions so formed fragment spontaneously in the gas phase, provided the emitter temperature is sufficiently high. The polystyrene chains rupture near their ends rather than in their centres, which is proposed to be a consequence of efficient charge delocalization. Following collisional activation, the polystyrene chains break up to give low-mass fragment ions. The low-mass fragment ions are proposed to be the result of successive depolymerization steps, following initial direct bond cleavage within the polymer chain.

scholarly journals Chemical Models of Collapsing Envelopes

2000 ◽  
Vol 197 ◽  
pp. 51-60
Author(s):  
Edwin A. Bergin
Keyword(s):  
Star Formation ◽  
Gas Phase ◽  
Chemical Evolution ◽  
Molecular Ions ◽  
Polar Molecules ◽  
Mass Star ◽  
Chemical Models ◽  
Gas Phase Molecules ◽  
Low Mass

We discuss recent models of chemical evolution in the developing and collapsing protostellar envelopes associated with low-mass star formation. In particular, the effects of depletion of gas-phase molecules onto grain surfaces is considered. We show that during the middle to late evolutionary stages, prior to the formation of a protostar, various species selectively deplete from the gas phase. The principal pattern of selective depletions is the depletion of sulfur-bearing molecules relative to nitrogen-bearing species: NH3 and N2H+. This pattern is shown to be insensitive to the details of the dynamics and marginally sensitive to whether the grain mantle is dominated by polar or non-polar molecules. Based on these results we suggest that molecular ions are good tracers of collapsing envelopes. The effects of coupling chemistry and dynamics on the resulting physical evolution are also examined. Particular attention is paid to comparisons between models and observations.

Characterization of Oligosaccharides of the Lactosamine Series Derived from Keratan Sulfates by Tandem Mass Spectrometry

2000 ◽  
Vol 6 (2) ◽  
pp. 193-203 ◽  
Author(s):  
Masayuki Kubota ◽  
Keiichi Yoshida ◽  
Akira Tawada ◽  
Mamoru Ohashi
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Bond Cleavage ◽  
The Other ◽  
Negative Ion ◽  
Ring Cleavage ◽  
Tandem Mass ◽  
Fragment Ions ◽  
Glycosidic Bond Cleavage

Positive- and negative-ion fast-atom bombardment tandem mass spectrometry with collision-induced dissociation (FAB-CID-MS/MS) has been used in the characterization of di-and tetra-saccharides of the lactosamine series from keratan sulfates. FAB-CID-MS/MS of Galβ1-4GlcNAc (L1) exhibited strong fragment ions originating from ring cleavage at the reducing-terminal sugar moiety together with glycosidic bond-cleavage ions, whereas GlcNAcβ1-3Gal (K1) showed strong glycosidic bond-cleavage ions but no ring-cleavage ions. A series of ring-cleavage fragment ions was observed with members of the L-series which have free hydroxyl groups at the C1 and C3 positions. CID-MS/MS spectra of the [M + Na – SO3]+ ion ( m/z 406) from L2 and the [M + Na − 2SO3]+ ion ( m/z 406) from L4 were almost identical with the CID-MS/MS spectrum of the [M + Na]+ ion ( m/z 406) from L1, which indicated that the sugar skeletons of L2 and L4 are the same as that of L1. On the other hand, the CID-MS/MS spectrum of the [M + Na – SO3]+ ion ( m/z 508) from L4 did not resemble that of the [M + Na]+ ion ( m/z 508) from L2. The former showed peaks that were additional to the peaks in the latter. Since these extra peaks were accounted for on the basis of the structure of L3 [Galβ1(6S)-4GlcNAc, S = sulfate], the in-source loss of sulfate groups by ester exchange upon FAB ionization takes place in a dual manner; one reaction at the non-reducing terminal sugar to give L2 and the other at the reducing-terminal sugar to give L3. The CID-MS/MS spectra were characteristic for the tetrasaccharides L1-L1, L2-L2 and L4-L4 while in-source fragmentation confirms the component disaccharides of each tetrasaccharide. The structure of a tetrasaccharide trisulfate was confirmed as L2–L4 and not L4–L2 by CID-MS/MS. Negative-ion FAB-CID-MS/MS spectra of the sulfated di-and tetra-saccharides showed a pattern similar to that of the positive-ion spectra. Subtraction of the CID-MS/MS spectrum of the [M – H]− ion of L2 [Galβ1-4GlcNAc(6S)] from that of the [M – H – SO3]− ion of L4 [Gal(6S)β1-4GlcNAc(6S)] gave several specific ions whose origins were nicely explained on the basis of the structure of L3. The structure of a pentasaccharide consisting of N-acetylneuraminic acid and a tetrasaccharide trisulfate was confirmed, on the basis of FAB-CID-MS/MS, as NeuNAcα2-6L2-L4.

Unimolecular Gas-Phase Reactions of Diethyl Phthalate, Isophthalate, and Terephthalate upon Electron Ionization

2003 ◽  
Vol 56 (5) ◽  
pp. 473 ◽  
Author(s):  
Susumu Tajima ◽  
Masashi Mamada ◽  
Satoshi Nakajima ◽  
Yutaka Takahashi ◽  
Nico M. M. Nibbering
Keyword(s):  
Gas Phase ◽  
Molecular Ions ◽  
Ion Source ◽  
Electron Ionization ◽  
Diethyl Phthalate ◽  
Gas Phase Reactions ◽  
Fragment Ions ◽  
Metastable Fragmentation ◽  
Primary Fragmentation ◽  
Ion Kinetic Energy

Unimolecular gas-phase reactions of diethyl phthalate (1), isophthalate (2), and terephthalate (3), upon electron ionization, have been investigated by use of mass-analyzed ion kinetic energy (MIKE) spectrometry and deuterium labelling. The metastable molecular ions (1)+ decompose to give exclusively the ions m/z 176 ([M – CH3CH2OH]+) and not the ions by the loss of CH3CH2O as proposed earlier in the literature. The metastable molecular ions (2)+ and (3)+ fragment differently from (1)+ and lead not only to the formation of the major fragment ions m/z 194 ([M − CH2CH2]+) via a McLafferty rearrangement but also to minor fragment ions m/z 193 ([M – CH2CH3]+).Yet, molecular ions decomposing in the ion source all show as primary fragmentation channel the loss of CH3CH2O to give the ions at m/z 177, which further dissociate to give the ions at m/z 149 through the loss of C2H4 or CO, indicating the resulting ions are +COC6H4COOH and +C6H4COOCH2CH3. The +COC6H4COOH ions decompose into the m/z 121, 93, and 65 ions by the consecutive losses of three carbon monoxide molecules, respectively. Prior to the second CO loss, a migration of the OH group to the benzene ring occurs. During the metastable fragmentation of the +C6H4COOCH2CH3 ions no ethoxy migration occurs, in contrast to the methoxy migration taking place in the metastable decomposition of the lower homologue +C6H4COOCH3 ions.

Der Einfluß der Kettenlänge auf die massenspektrometrigche Fragmentierung höherer 1.ω-Diphenylalkane / The Influence of the Chain Length on the Mass Spectrometric Fragmentation of Higher 1, ω-Diphenylalkanes

1979 ◽  
Vol 34 (12) ◽  
pp. 1750-1764 ◽  
Author(s):  
Dietmar Kuck ◽  
Hans-Friedrich Grützmacher
Keyword(s):  
Gas Phase ◽  
Chain Length ◽  
Hydrogen Exchange ◽  
Molecular Ions ◽  
Mass Spectrometric ◽  
Exchange Reactions ◽  
Fragment Ions ◽  
Competitive Reactions ◽  
Solvated Ions ◽  
Mass Spectrometric Fragmentation

The mass spectrometric fragmentation of 1,ω-diphenylalkanes (2 ≤ ω ≤ 22) has been studied in order to elucidate the effect of the chain length on the reactions of unstable and metastable molecular ions with respect to the occurrence of internally solvated ions in the gas phase. The unstable molecular ions of all 1,ω-diphenylalkanes react predominantly by formation of C7H7+ and C7H8+ ions, the latter ones are also formed by metastable molecular ions. Neither the variation of the relative abundances of these fragment ions with the chain length nor the fragmentation of specifically deuterated molecular ions indicate any internal solvation in the reacting ions. Inspite of the localized activated C-H bonds at the benzylic positions, these “activated” H atoms are not involved in intra­molecular hydrogen exchange reactions or the formation of C7H8+ ions (with the exception of ω = 3). Especially the higher homologues (co ≿ 12) react very similarly to the molecular ions of 1-phenylalkanes, while the fragmentation of the lower homologues (co ≲ 6) is determined by specific (“vinculoselective”) competitive reactions, e.g. loss of C7H7 and C8H8.

Liquid Secondary Ion Mass Spectrometry and Collision-induced Dissociation Mass Spectrometry of Sulfonamide Derivatives of meso-Tetraphenylporphyrin

1999 ◽  
Vol 03 (03) ◽  
pp. 172-179 ◽  
Author(s):  
M. ROSÁRIO M. DOMINGUES ◽  
M. GRAÇA SANTANA-MARQUES ◽  
A. J. FERRRER-CORREIA ◽  
AUGUSTO C. TOMÉ ◽  
MARIA G. P. M. S. NEVES ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Secondary Ion Mass Spectrometry ◽  
Molecular Ions ◽  
Collision Induced Dissociation ◽  
Fragment Ions ◽  
Ion Mass Spectrometry ◽  
Derivatives Of ◽  
Secondary Ion

Liquid secondary ion mass spectrometry (LSIMS) and collision-induced dissociation (CID) were used for the characterization of sulfonamide derivatives of meso-tetraphenylporphyrin (TPP). The spectra obtained using LSIMS show abundant molecular ions and fragment ions from losses of the sulfonamide moieties. The main fragmentation observed in the LSI mass spectra and in the CID spectra of the protonated or cationized molecules involves the loss of one sulfonamide group. In addition, in the CID spectra of these compounds the fragment ions formed by the elimination of two, three and/or four sulfonamide groups are also observed. The CID spectra of the protonated or cationized molecules of these derivatives do not display the ions formed by the cleavage of the S - N bond which have been reported for other sulfonamide compounds. The LSI mass spectra and CID spectra of sulfonamide derivatives of meso-tetraphenylporphyrin provide an easy and reliable means of identification of the number and nature of sulfonamide groups in the porphyrinic ring.

Elucidating the Fragmentation Mechanism of Protonated Lewis A Trisaccharide using MSn CID

2021 ◽  
pp. 146906672110690
Author(s):  
Volker Iwan ◽  
Jürgen Grotemeyer
Keyword(s):  
Gas Phase ◽  
Main Product ◽  
Bond Cleavage ◽  
Mass Analyzer ◽  
Blood Group Antigens ◽  
Fragmentation Mechanism ◽  
Esi Ms ◽  
Fragment Ions ◽  
Glycosidic Bond Cleavage ◽  
Lewis A

Lewis blood group antigens are a prominent example of isomeric oligosaccharides with biological activity. Understanding the fragmentation mechanism in the gas phase is essential for their identification and assignment by mass spectrometric methods such as ESI-MS. In this work, the [M + H]+ species of Lewis A trisaccharide and Lewis A trisaccharide methyl glycoside were studied by ESI-MS with FT-ICR as mass analyzer with respect to their fragmentation mechanism. The comparison between the underivatized and the methylated species has shown that the reducing end plays a key role in this mechanism. The results of this study question the existence of Z-type fragment ions after activation of the protonated species. The main product of the fragmentation are Y-type fragment ions and a combination of Y-type fragmentation and the loss of water at the reducing end instead of Z-type fragmentation. C-type fragment ions could not be detected. MS3 measurements also reveal that each fragment ion only occurs with the participation of a mobile proton and the possibility of glycosidic bond cleavage after fragmentation has already occurred at the reducing end as B2 fragment ion.

Preparation and properties of mononuclear vanadium thiolates: structural characterization of the [V(SBu-tert)4]0,- pair and carbon-sulfur bond cleavage in V(SBu-tert)4 in the gas phase

1991 ◽  
Vol 30 (2) ◽  
pp. 300-305 ◽  
Author(s):  
Dwight D. Heinrich ◽  
Kirsten. Folting ◽  
John C. Huffman ◽  
John G. Reynolds ◽  
George. Christou
Keyword(s):  
Gas Phase ◽  
Structural Characterization ◽  
Bond Cleavage ◽  
Sulfur Bond

Hydrogen atom attachment to histidine and tryptophan containing peptides in the gas phase

2019 ◽  
Vol 21 (22) ◽  
pp. 11633-11641 ◽  
Author(s):  
Daiki Asakawa ◽  
Hidenori Takahashi ◽  
Shinichi Iwamoto ◽  
Koichi Tanaka
Keyword(s):  
Hydrogen Atom ◽  
Gas Phase ◽  
Bond Cleavage ◽  
Tryptophan Residue ◽  
Side Chains ◽  
Hydrogen Atoms ◽  
Fragment Ions ◽  
Gas Phase Fragmentation

In this study, we focus on the gas-phase fragmentation induced by the attachment of hydrogen atoms to the histidine and tryptophan residue side-chains in the peptide that provides the fragment ions due to Cα–Cβ bond cleavage.

Radiation less transitions in gas phase molecular ions

1980 ◽  
Vol 77 ◽  
pp. 705-718 ◽  
Author(s):  
Sydney Leach ◽  
Gérald Dujardin ◽  
Guy Taieb
Keyword(s):  
Gas Phase ◽  
Molecular Ions
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