On the concomitant crystallization of amino acid crystals upon dissolution of some amino acid salt crystals

Contains fulltext : 140110.pdf (publisher's version ) (Open Access

Reaction Mechanisms of Collision and Electron Induced Peptide Dissociation Revealed by Ion Spectroscopy

Contains fulltext : 201542.pdf (publisher's version ) (Open Access)Radboud University, 19 maart 2019Promotor : Oomens, J. Co-promotor : Martens, J.K.iv, 244 p

Deamidation reactions of protonated asparagine and glutamine investigated by ion spectroscopy

Contains fulltext : 156945pos.pdf (postprint version ) (Open Access

Deamidation Reactions of Asparagine- and Glutamine-Containing Dipeptides Investigated by Ion Spectroscopy

Contains fulltext : 161495.pdf (publisher's version ) (Open Access

Deamidation of Protonated Asparagine-Valine Investigated by a Combined Spectroscopic, Guided Ion Beam, and Theoretical Study

Contains fulltext : 190029.pdf (publisher's version ) (Open Access

Dehydration reactions of protonated dipeptides containing asparagine or glutamine investigated by infrared ion spectroscopy

The role of specific amino acid side-chains in the fragmentation chemistry of gaseous protonated peptides resulting from collisional activation remains incompletely understood. For small peptides containing asparagine and glutamine, a dominant fragmentation channel induced by collisional activations is, in addition to deamidation, the loss of neutral water. Identifying the product ion structures from H2O-loss from four protonated dipeptides containing Asn or Gln using infrared ion spectroscopy, mechanistic details of the dissociation reactions are revealed. Several sequential dissociation reactions have also been investigated and provide additional insights into the fragmentation chemistry. While water loss can in principle occur from the C-terminus, the side chain or the amide bond carbonyl oxygen, in most cases the C-terminus was found to detach H2O, leading to a b2-sequence ion with an oxazolone structure for AlaGln, and bifurcating mechanisms leading to both oxazolone and diketopiperazine species for AlaAsn and AsnAla. In contrast, GlnAla expels water from the amide side chain leading to an imino-substituted prolinyl structure

Spectroscopic Characterization of an Extensive Set of c-Type Peptide Fragment Ions Formed by Electron Transfer Dissociation Suggests Exclusive Formation of Amide Isomers

Electron attachment dissociation (electron capture dissociation (ECD) and electron transfer dissociation (ETD)) applied to gaseous multiply protonated peptides leads predominantly to backbone N–Cα bond cleavages and the formation of c- and z-type fragment ions. The mechanisms involved in the formation of these ions have been the subject of much discussion. Here, we determine the molecular structures of an extensive set of c-type ions produced by ETD using infrared ion spectroscopy. Nine c3- and c4-ions are investigated to establish their C-terminal structure as either enol-imine or amide isomers by comparison of the experimental infrared spectra with quantum-chemically predicted spectra for both structural variants. The spectra suggest that all c-ions investigated possess an amide structure; the absence of the NH bending mode at approximately 1000–1200 cm–1 serves as an important diagnostic feature