Fig. 3. Structures of synthetic disaccharides, polysaccharide and tetrasaccharides for structural analysis. Panel A shows eight ¹³C-labeled HS disaccharides. These disaccharides are used for the disaccharide analysis of HS. “*” indicates the ¹³C-labeling site. The disaccharides are prepared from oligosaccharides carrying site-specifically labeled ¹³C-labeled GlcA residues. Panel B shows the schematic structure of ¹³C-labeled N-sulfo heparosan that is used as a recovery calibrant. The polysaccharide is susceptible to the degradation of heparin lyases to yield disaccharide ΔIVS, but its molecular mass is 12 Da higher than the native counterpart. Panel C shows the structures of three 3-O-sulfated tetrasaccharides and one 3-O-sulfated disaccharide.