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Updated: May 23, 2026

Determination of the Gas-phase Acidities of Oligopeptides
Published on: June 24, 2013
Conformation-specific spectroscopy of peptide fragment ions in a low-temperature ion trap
Tobias N Wassermann1, Oleg V Boyarkin, Béla Paizs
1Laboratoire de Chimie Physique Moléculaire, École Polytechnique Fédérale de Lausanne, 1015, Lausanne, Switzerland.
Abstract:
We have applied conformer-selective infrared-ultraviolet (IR-UV) double-resonance photofragment spectroscopy at low temperatures in an ion trap mass spectrometer for the spectroscopic characterization of peptide fragment ions. We investigate b- and a-type ions formed by collision-induced dissociation from protonated leucine-enkephalin. The vibrational analysis and assignment are supported by nitrogen-15 isotopic substitution of individual amino acid residues and assisted by density functional theory calculations. Under such conditions, b-type ions of different size are found to appear exclusively as linear oxazolone structures with protonation on the N-terminus, while a rearrangement reaction is confirmed for the a (4) ion in which the side chain of the C-terminal phenylalanine residue is transferred to the N-terminal side of the molecule. The vibrational spectra that we present here provide a particularly stringent test for theoretical approaches.
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