Sequence analysis of highly sulfated, heparin-derived oligosaccharides using fast atom bombardment mass spectrometry

Heparin, a polydisperse, sulfated copolymer of 1----4 linked glucosamine and uronic acid residues, has been used clinically as an anticoagulant for half a century. Despite a yearly use of over 50 million doses in the U.S. alone, heparin's exact chemical structure remains unclear. The negative ion fast atom bombardment mass spectrometry (FAB-MS) analysis is presented for a series of enzymatically prepared, homogeneous, structurally characterized, highly sulfated, heparin-derived oligosaccharides using triethanolamine as the FAB matrix. In addition to the clear presence of monoanionic sodiated molecular ions, structurally significant (sequence) fragment ions are observed and characterized with respect to the known structure for five of the heparin-derived oligosaccharides. The structure of a sixth oligosaccharide is predicted by using negative ion FAB-MS and subsequently confirmed by chemical, enzymatic, and NMR spectroscopic methods.