Premium
Kinetics of gas‐phase hydrogen/deuterium exchange and gas‐phase structure of protonated phenylalanine, proline, tyrosine and tryptophan
Author(s) -
Rožman Marko,
Kazazić Saša,
Klasinc Leo,
Srzić Dunja
Publication year - 2003
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.1261
Subject(s) - chemistry , protonation , hydrogen–deuterium exchange , phenylalanine , deuterium , fourier transform ion cyclotron resonance , tryptophan , proton affinity , affinities , mass spectrometry , ion cyclotron resonance , proton , hydrogen bond , amino acid , hydrogen , analytical chemistry (journal) , stereochemistry , crystallography , ion , molecule , organic chemistry , chromatography , cyclotron , biochemistry , physics , quantum mechanics
Site‐specific rate constants for the gas‐phase hydrogen/deuterium (H/D) exchange of four, three, five and five hydrogen atoms in protonated phenylalanine (Phe), proline (Pro), tyrosine (Tyr) and tryptophan (Trp), respectively, were determined from matrix‐assisted laser desorption/ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI‐FTICRMS) experiments with D 2 O, D 2 S, and CH 3 OD as deuterating agents. No H/D exchange was observed with D 2 S. For exchange with both CD 3 OD and D 2 O, which is about ten times slower in the latter, results indicate for all compounds protonation of the α ‐amino group in agreement with theoretical results. Also, with both reagents, all compounds exchange at the COOH site more than ten times faster than at the protonation site, with OH and NH sites of Tyr and Trp, respectively, exchanging slowest. The observation of H/D exchange despite the high differences in proton affinities between the amino acids and deuterating agent exceeding 200 kJ mol −1 is in agreement with lowering of the barrier for proton transfer through hydrogen bonding proposed by Lebrilla and coworkers. Copyright © 2003 John Wiley & Sons, Ltd.