Benefits of Ion Mobility Separation and Parallel Accumulation-Serial Fragmentation Technology on timsTOF Pro for the Needs of Fast Photochemical Oxidation of Protein Analysis.

Fast photochemical oxidation of proteins (FPOP) is a recently developed technique for studying protein folding, conformations, interactions, etc. In this method, hydroxyl radicals, usually generated by KrF laser photolysis of HO, are used for irreversible labeling of solvent-exposed side chains of amino acids. Mapping of the oxidized residues to the protein's structure requires pinpointing of modifications using a bottom-up proteomic approach. In this work, a quadrupole time-of-flight (QTOF) mass spectrometer coupled with trapped ion mobility spectrometry (timsTOF Pro) was used for identification of oxidative modifications in a model protein. Multiple modifications on the same residues, including six modifications of histidine, were successfully resolved. Moreover, parallel accumulation-serial fragmentation (PASEF) technology allows successful sequencing of even minor populations of modified peptides. The data obtained indicate a clear improvement of the quality of the FPOP analysis from the viewpoint of the number of identified peptides bearing oxidative modifications and their precise localization. Data are available via ProteomeXchange with identifier PXD020509.