Gas phase ion chemistry of biomolecules. Part 37 - Gas-phase reactions of protonated tryptophan
Details
Publication Year 2004-01, Volume 15, Issue #1, Page 65-76
Journal Title
JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
Publication Type
Journal Article
Abstract
The gas phase reactions of protonated tryptophan have been examined in a quadrupole ion trap using a combination of collision induced dissociation, hydrogen-deuterium exchange, regiospecific deuterium labeling and molecular orbital calculations (at the B3LYP/6-31G* level of theory). The loss of ammonia from protonated tryptophan is observed as the primary fragmentation pathway, with concomitant formation of a [M + H - NH3](+) ion by nucleophilic attack from the C3 position of the indole side chain. Hydrogen-deuterium exchange and regiospecific deuterium labeling reveals that scrambling of protons in the C2 and C4 positions of the indole ring, via intramolecular proton transfer from the thermodynamically preferred site of protonation at the amino nitrogen, precedes ammonia loss. Molecular orbital calculations have been employed to demonstrate that the activation barriers to intramolecular proton transfer are lower than that for NH3 loss.
Publisher
ELSEVIER SCIENCE INC
Keywords
HYDROGEN-DEUTERIUM EXCHANGE; ALPHA-AMINO-ACIDS; FAST-ATOM-BOMBARDMENT; MASS-SPECTROMETRY; FRAGMENTATION REACTIONS; NEIGHBORING GROUP; AB-INITIO; PEPTIDES; DERIVATIVES; MOLECULES
Rights Notice
Refer to copyright notice on published article.


Creation Date: 2004-01-01 12:00:00
Last Modified: 0001-01-01 12:00:00
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