High-Energy Photon Activation Tandem Mass Spectrometry Provides Unprecedented Insights into the Structure of Highly Sulfated Oligosaccharides Extracted from Macroalgal Cell Walls

2015 ◽  
Vol 87 (2) ◽  
pp. 1042-1049 ◽  
Author(s):  
David Ropartz ◽  
Alexandre Giuliani ◽  
Cécile Hervé ◽  
Audrey Geairon ◽  
Murielle Jam ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Tandem Mass Spectrometry ◽  
Cell Walls ◽  
High Energy ◽  
Tandem Mass ◽  
Photon Activation ◽  
High Energy Photon ◽  
Energy Photon ◽  
Sulfated Oligosaccharides

High Energy Photon Activation

2016 ◽  
Author(s):  
L. Kosta ◽  
M. Dermelj ◽  
J. Slunečko
Keyword(s):  
High Energy ◽  
Photon Activation ◽  
High Energy Photon ◽  
Energy Photon

The decarbonylation of ionized β-hydroxypyruvic acid: the hydrogen-bridged radical cation [CH2=O . . .H . . .==C-OH].+ studied by experiment and theory

1998 ◽  
Vol 76 (3) ◽  
pp. 335-349 ◽  
Author(s):  
Lorne M Fell ◽  
Peter C Burgers ◽  
Paul JA Ruttink ◽  
Johan K Terlouw
Keyword(s):  
Mass Spectrometry ◽  
Methyl Ester ◽  
Tandem Mass Spectrometry ◽  
Ab Initio ◽  
Radical Cation ◽  
Glycolic Acid ◽  
High Energy ◽  
Low Energy ◽  
Tandem Mass ◽  
Low Energy Ions

The intriguing gas-phase ion chemistry of β-hydroxypyruvic acid (HPA), HOCH2C(==O)COOH, has been investigated using tandem mass spectrometry (metastable ion (MI) and (multiple) collision-induced dissociation (CID) experiments, neutralization-reionization mass spectrometry (NRMS), 18O and D isotopic labelling on both the acid and its methyl ester) in conjunction with computational chemistry (ab initio MO and density functional theories). HPA does not enolize upon evaporation, but it retains its keto structure. When ionized, decarbonylation occurs and, depending on the internal-energy content, this dissociation reaction proceeds via two distinct routes. The source-generated, high-energy ions lose the keto C==O, not via a least-motion extrusion into ionized glycolic acid, HOCH2COOH.+ , but via a rearrangement that yields the title H-bridged radical cation CH2==O ... H ... O==C-OH.+ for which Δ Hf0 = 99 ± 3 kcal/mol. The long-lived low-energy ions enolize prior to decarbonylation and lose the carboxyl C==O. Again, this is not a least-motion extrusion (which would produce the most stable isomer, HOC(H)==C(OH)2.+ Δ Hf0 = 73 kcal/mol) but a rearrangement yielding the ion-dipole complex HOC(H)C==C==O.+/H2O. The methyl ester of HPA behaves analogously, yielding CH2==O... H ...O==C-OCH3.+ and HOC(H)C==C==O.+ / CH3OH upon decarbonylation of the high- and low-energy ions, respectively. Decarboxylation into the ylidion CH2OH2.+ characterizes the dissociation chemistry of both the title H-bridged ion and its glycolic acid isomer HOCH2COOH.+ . A computational analysis of this reaction (which satisfies the experimental observations) leads to the proposal that the decarboxylation of the acid occurs via CH2-O(H) ... H ... ==C==O.+ as the key intermediate, whereas the title H-bridged ion follows a higher energy route that involves ion-dipole rotations leading to the ionized carbene HO(H2)CO-C-OH.+ and the distonic ion H2O-C(H2)-O-C==O.+ as key intermediates.Key words: tandem mass spectrometry, hydrogen-bridged radical cation, hydroxypyruvic acid, ab initio calculations, keto-enol tautomerization, 18O labelling.

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