Cold atmospheric plasma (CAP) sources can be used to produce a multitude of different reactive species in a spatially and time resolved manner leading to a wide variety of modifications on nearly all amino acids . CAP thus has the ability to alter the activity of proteins or enzymes in cellular signalling pathways, which could be one mechanism in the treatment of chronic wounds that is strongly modulated by reactive species signalling .
The aim of this study was to determine which oxidative PTMs on three model peptides are generated by the treatment with two different plasma sources (kINPen  and COST jet ). Nano-LC/High resolution mass-spectrometry was performed and data were analysed by a software algorithm allowing to search for various PTMs simultaneously. Significant differences in the modification pattern were observed. While the COST jet modified predominantly aromatic amino acids (AA), the kINPen led also to the oxidation of aliphatic AA and showed a substantial nitration of aromatics. The nitration of such an aromatic AA like tyrosine in the enzyme aldolase A can lead to a regulation of mast cell degranulation, an important regulator in wound healing processes . Additionally, the chemical environment of a given AA determined its reactivity. Trioxidations and the modification 3O-NHCO  can only be found on histidine during direct argon treatments. Phenylalanine in the middle of a peptide shows massively increased oxidations and dioxidations compared to another phenylalanine, which is closer to the C-terminus.
Ten further peptides were designed in a way that each AA occurs with various neighbouring AA providing a different chemical environment found to modulate the observable modifications. Thus, a comprehensive library of plasma-derived oxidative modifications will be created that consequently will be used to predict and identify modifications of proteins in complex settings such as chronic wounds under oxidant conditions.