Enhancing Biomolecule Analysis and 2DMS Experiments by Implementation of (Activated Ion) 193 nm UVPD on a FT-ICR Mass...

Ultraviolet photodissociation is a fast, photon-mediated fragmentation method that yields high sequence coverage and informative cleavages of biomolecules. In this work, 193 nm UVPD was coupled with a 12 Tesla FT-ICR mass spectrometer and 10.6 μm infrared multi-photon dissociation to provide gentle slow-heating of UV-irradiated ions. No internal instrument hardware modifications were required. Adjusting the timing of laser pulses to the ion motion within the ICR cell provided consistent fragmentation yield shot-to-shot and may also be used to monitor ion positions within the ICR cell. Single-pulse UVPD of the native-like 5+ charge state of ubiquitin resulted in 86.6% cleavage coverage. Additionally, IR activation post UVPD doubled the overall fragmentation yield and boosted the intensity of UVPD-specific x-type fragments up to 4-fold. This increased yield effect was also observed for the 6+ charge state of ubiquitin, albeit less pronounced. This indicates that gentle slow-heating serves to sever tethered fragments originating from non-covalently linked compact structures and makes activation post UVPD an attractive option to boost fragmentation efficiency for top-down studies. Lastly, UVPD was implemented and optimized as a fragmentation method for 2DMS, a data-independent acquisition method. UVPD-2DMS was demonstrated to be a viable method using BSA digest peptides as a model system.