O-linked glycosylation of ADAMTS13.O-linked glycosylation starts with a GalNAc attached to either a serine or a threonine; glycan moieties such as galactose, fucose, GlcNAc, GalNAc, or sialic acid are added subsequently. There is no consensus on the composition of these structures, and the presented structures are possibilities corresponding to the residues identified by the MS and Byonic software. (A) Possible glycan structures that correspond to the glycan moieties identified using the Byonic software. Our MS approach is not able to distinguish between different hexoses (such as mannose, glucose, or galactose) or HexNAcs (such as GlcNAc and GalNAc); the presented structures are based on our current knowledge of the biosynthetic pathway of O-glycans. (B) Amino acid position (serine or threonine) and the corresponding domain of ADAMTS13 and glycan elements are identified on this position as determined using Byonic software.