Conformational Characterization of Peptides and Proteins by 193 nm Ultraviolet Photodissociation in the Collision Cell of a Trapped Ion Mobility Spectrometry-Time-of-Flight Mass Spectrometer

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