BMSO (bismaleimide sulfoxide) crosslinker is a homobifunctional, cysteine residue-targeting, sulfoxide-containing crosslinker for analysis of protein-protein interactions (PPIs) through crosslinking mass spectrometry (XL-MS). BMSO possesses two maleimide reactive groups for targeting Cys, a 24.2 Å spacer arm, and two symmetrical C-S cleavable bonds adjacent to the central sulfoxide. While similar reagents react with lysine (Lys) and acidic residues, targeting Cys provides further opportunity to characterize protein interaction surfaces. Additionally, the post-cleavage spacer yields tagged peptides for unambiguous identification by collision-induced dissociation in tandem MS.
BMSO crosslinker provides complementary data to amine-reactive and acidic residue-targeting reagents and will find wide utility in the elucidation of PPIs, study of proteins that function as complexes, quantification of structural dynamics, and the quest for targeting "undruggable" protein targets.