Fragmentation reactions of singly and doubly charged alkali metal ion–peptide complexes: A reaction specific to C-terminal arginine residues
✍ Scribed by Xue-Jun Tang; Pierre Thibault; Robert K. Boyd
- Publisher
- John Wiley and Sons
- Year
- 1993
- Tongue
- English
- Weight
- 604 KB
- Volume
- 28
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
Ionspray ionization of solutions containing peptides (M) plus alkali metal ions X+ produces ( M + XI +, [ M + H + XI *+ and [ M + 2x1 *+ ions. Low-energy collision-induced dissociation of these species demonstrated a marked trend towards decreased strength of the M-X+ interaction with increasing size of X+. For example, the [ M + 2X1*+ species yield predominantly [ M + XI + plus X+ for X+ = K + , Rb', Cs', but rich spectra of fragment ions incorporating X+ when X + = Li+ or Na'. In general, these fragmentation reactions correspond to those established previously for the corresponding [ M + XI + precursors, including formation of ( bi + X + OH] + and [ bi + X -HI + fragments. As a special case, complexes of Li+ or Na+ with peptides having Arg (but not Lys or other basic residues) at the C-terminus undergo a facile loss of 60 u. The resulting [ M + X -601 + ions also fragment further to yield (y,' + X -601 + fragments. Characterization of the 60 u neutral loss was undertaken by using tandem mass spectrometry plus hydrogedeuterium exchange, and a mechanism is proposed to account for the characteristics of the process.