193 nm ultraviolet photodissociation for the characterization of singly charged proteoforms generated by MALDI

Abstract

MALDI imaging allows for the near-cellular profiling of proteoforms directly from microbial colonies, or plant and mammalian tissues. Despite detecting hundreds of proteoforms, identification of unknowns with only intact mass information remains a distinct challenge, even at with high resolution and mass accuracy. To this end many supplementary methods have been used to create experimental databases for accurate mass matching, including bulk or spatially resolved bottom-up and/or top-down proteomics. Herein we describe the application of 193 nm ultraviolet photodissociation (UVPD) for fragmentation of quadrupole isolated singly charged ubiquitin (m/z 8565) by MALDI-UVPD on an UHMR HF Orbitrap. This platform permitted the high-resolution accurate mass measurement of not just terminal fragments, but also large internal fragments. The outlined workflow demonstrated the feasibility of high resolution top-down analysis of MALDI generated protein ions and the potential towards more comprehensive characterization of proteoforms in MALDI imaging applications.