UVPD of two different conformational arrangements of [M + 6H]6+ ubiquitin. (a) UVPD spectra obtained at a cone voltage of 10 V (blue, bottom spectrum) and a cone voltage of 120 V (red, top spectrum). (b) Arrival time distribution as a function of cone voltage ranging from 10 to 120 V. (c) UVPD cleavage sites indicated on the crystal structure (PDB structure 4Z9S) of ubiquitin. Sites with higher relative cleavage abundance in the “soft” spectra are colored blue; those with higher abundance in the “harsh” condition are marked red.219 Reprinted with permission from Theisen, A.; Black, R.; Corinti, D.; Brown, J. M.; Bellina, B.; Barran, P. E. Initial Protein Unfolding Events in Ubiquitin, Cytochrome c and Myoglobin Are Revealed with the Use of 213 Nm UVPD Coupled to IM-MS. J. Am. Soc. Mass Spectrom. 2019, 30, 24–33. Copyright 2019 Springer Nature.