Pille, LauraLauraPilleOrtiz Mahecha, CarlosCarlosOrtiz MahechaOostenrijk, BartBartOostenrijkLeroux, JulietteJulietteLerouxGirod, MarionMarionGirodHirsch, KonstantinKonstantinHirschMacAleese, LukeLukeMacAleeseMeißner, RobertRobertMeißnerScuderi, DeboraDeboraScuderiUnger, IsaakIsaakUngerZamudio-Bayer, VicenteVicenteZamudio-BayerBari, SadiaSadiaBariSchwob, LucasLucasSchwob2026-04-152026-04-152026Chemistry A European Journal (in Press): (2026)https://hdl.handle.net/11420/62655Non-covalent sulfur–aromatic ((Formula presented.)) interactions play a crucial role in stabilizing the structure of proteins and have been associated with neurodegenerative diseases. We investigated the influence of the (Formula presented.) interaction on the electronic structure and fragmentation behavior of sequence-isomer model peptides by means of ultraviolet photodissociation (UVPD) and near-edge x-ray absorption mass spectrometry (NEXAMS). The studies revealed distinct fragmentation behavior for one of the model peptides under both valence and core–shell electronic excitation, with characteristic fragmentation channels that serve as potential fingerprints of sulfur–aromatic interactions. Moreover, core–shell excitations at the carbon K-edge revealed significant shifts between the (Formula presented.) peptide and the control peptides in the aromatic (Formula presented.) transitions, indicating changes in the electronic structure due to (Formula presented.) interactions. Enhanced sampling molecular dynamics and quantum mechanical calculations reveal the influence of the sulfur orientation, providing insights into the fundamental nature of (Formula presented.) interactions.en1521-37652026Wileyhttps://creativecommons.org/licenses/by/4.0/conformational analysisNEXAFSNEXAMSnoncovalent interactionspeptidesS⋯π$S\cdots \pi$ interactionsUVPDx-ray action spectroscopyNatural Sciences and Mathematics::540: ChemistryJournal Articlehttps://doi.org/10.15480/882.1697110.1002/chem.20250348310.15480/882.16971