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 N and O K-edges was employed ongas-phase peptides to probe the electronic transitions related totheir protonation sites, namely at basic side chains, the N-terminus and the amide oxygen.

Radiation‐Induced Molecular Processes in DNA: A Perspective on Gas‐Phase Interaction Studies

“…Here, protonation of a nucleobase N‐site transforms an imine‐group into an amine‐group and the resulting N 1s shift leads to a shifted X‐ray absorption resonance that can be selectively adressed. Site‐selective photoionization of complex gas‐phase biomolecules currently is a rapidly growing field [14–17] …”

“…Site-selective photoionization of complex gas-phase biomolecules currently is a rapidly growing field. [14][15][16][17] The oligonucleotide conformation can in principle be determined and selected prior to the interaction process, using established techniques such as for instance ion-mobility spectrometry (IMS), where the drift velocity of a molecular ion through a gas is related to its geometric cross section and thus to its conformation. Even though this technology is routinely applied in the field of mass spectrometry, its use for e. g. soft Xray interaction studies with biomolecular ions is far from being straightforward, for instance because conformer selection further reduces the already low ESI signal.…”