Issue 37, 2023

Mapping the electronic transitions of protonation sites in peptides using soft X-ray action spectroscopy

Abstract

Near-edge X-ray absorption mass spectrometry (NEXAMS) around the nitrogen and oxygen K-edges was employed on gas-phase peptides to probe the electronic transitions related to their protonation sites, namely at basic side chains, the N-terminus and the amide oxygen. The experimental results are supported by replica exchange molecular dynamics and density-functional theory and restricted open-shell configuration with single calculations to attribute the transitions responsible for the experimentally observed resonances. We studied five tailor-made glycine-based pentapeptides, where we identified the signature of the protonation site of N-terminal proline, histidine, lysine and arginine, at 406 eV, corresponding to N 1s → σ*(NHx+) (x = 2 or 3) transitions, depending on the peptides. We compared the spectra of pentaglycine and triglycine to evaluate the sensitivity of NEXAMS to protomers. Separate resonances have been identified to distinguish two protomers in triglycine, the protonation site at the N-terminus at 406 eV and the protonation site at the amide oxygen characterized by a transition at 403.1 eV.

Graphical abstract: Mapping the electronic transitions of protonation sites in peptides using soft X-ray action spectroscopy

Supplementary files

Article information

Article type
Paper
Submitted
31 May 2023
Accepted
16 Aug 2023
First published
18 Sep 2023
This article is Open Access
Creative Commons BY license

Phys. Chem. Chem. Phys., 2023,25, 25603-25618

Mapping the electronic transitions of protonation sites in peptides using soft X-ray action spectroscopy

J. Leroux, A. Kotobi, K. Hirsch, T. Lau, C. Ortiz-Mahecha, D. Maksimov, R. Meißner, B. Oostenrijk, M. Rossi, K. Schubert, M. Timm, F. Trinter, I. Unger, V. Zamudio-Bayer, L. Schwob and S. Bari, Phys. Chem. Chem. Phys., 2023, 25, 25603 DOI: 10.1039/D3CP02524A

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