Gas phase H/D (hydrogen/deuterium) exchange rates of proline-containing peptides were studied using electrospray ionization ion trap mass spectrometry.  Proline peptides were chosen for study because proline's side chain forms a 5-membered ring that restricts conformation.  Studying in the gas phase eliminates solvent effects, allowing for the study of only intramolecular interactions.  Proline substitution accelerates exchange in pentapeptides, and the impact is greatest when near the C-terminus, except when at the second position, where it slows exchange. Electronic structure calculations were used to investigate proline's effect on the energetics of exchange of the amine and carboxylic acid hydrogens.  Calculations indicate that amine exchange has a lower energy barrier for Gly-Pro-Pro than Gly-Gly-Gly, while carboxylic acid exchange is energetically similar for both peptides.   Preliminary calculations with proline-substituted pentapeptides suggest that amine relay exchange is much more energetically favorable if D2O can coordinate two carbonyls.

Hydrogen/deuterium exchange and computational modeling of proline-containing peptides in the gas phase

243rd National Meeting (2012)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.