UV Photodissociation Mass Spectrometry Accurately Localize Sites of Backbone Deuteration in Peptides.

Hydrogen/deuterium exchange mass spectrometry (HDX-MS) is now a routinely used technique to inform on protein structure, dynamics, and interactions. Localizing the incorporated deuterium content on a single residue basis increases the spatial resolution of this technique enabling detailed structural analysis. Here, we investigate the use of ultraviolet photodissociation (UVPD) at 213 nm to measure deuterium levels at single residue resolution in HDX-MS experiments. Using a selectively labeled peptide, we show that UVPD occurs without H/D scrambling as the peptide probe accurately retains its solution-phase deuterium labeling pattern. Our results indicate that UVPD provides an attractive alternative to electron mediated dissociation for increasing the spatial resolution of the HDX-MS experiment, capable of yielding high fragmentation efficiency, high fragment ion diversity, and low precursor ion charge-state dependency.