Conformational\nCharacterization of Peptides and Proteins\nby 193 nm Ultraviolet Photodissociation in the Collision Cell of a\nTrapped Ion Mobility Spectrometry-Time-of-Flight Mass Spectrometer

Ultraviolet photodissociation (UVPD) has been shown to\nbe a versatile\nion activation strategy for the characterization of peptides and intact\nproteins among other classes of biological molecules. Combining the\nhigh-performance mass spectrometry (MS/MS) capabilities of UVPD with\nthe high-resolution separation of trapped ion mobility spectrometry\n(TIMS) presents an opportunity for enhanced structural elucidation\nof biological molecules. In the present work, we integrate a 193 nm\nexcimer laser in a TIMS-time-of-flight (TIMS-TOF) mass spectrometer\nfor UVPD in the collision cell and use it for the analysis of several\nmass-mobility-selected species of ubiquitin and myoglobin. The resultant\ndata displayed differences in fragmentation that could be correlated\nwith changes in protein conformation. Additionally, this mobility-resolved\nUVPD strategy was applied to collision-induced unfolded ions of ubiquitin\nto follow changes in fragmentation patterns relating to the extent\nof protein unfolding. This platform and methodology offer new opportunities\nfor exploring how conformational variations are manifested in the\nfragmentation patterns of gas-phase ions.