Oligosaccharides, structure determination

Short review of the uses of MALDI MS and tandem MS in oligosaccharide structure determination. 

Figure 14.2 Representative oligosaccharide structures found on mammalian glycoproteins and glycolipids. The complex oligosaccharides may be bi-, tri-, or tetra-antennary the branches may be more or less elongated with 1—>4 linked lactosamine units, and they may or may not be sialylated. The SLex, Lea, and Leb structures represent the different blood group determinants often present on lipids, and the elongated core 2 structure is a mucin-type glycosylation. Proteoglycans have a common core to which a variety of linear acidic polysaccharides are attached.

Harvey, D.J. Naven, T.J.P. Ktister, B. Bateman, R. Green, M.R. Critchley, G. Comparison of Fragmentation Modes for the Structural Determination of Complex Oligosaccharides Ionized by MALDl-MS. Rapid Commun. Mass Spectrom. 1995, 9, 1556-1561. 

Duus J0, Gotfredsen CH, Bock K (2000) Carbohydrate Structural Determination by NMR Spectroscopy Modem Methods and Limitations. Chem Rev 100 4589 Agrawal PK, Pathak AK (1996) Nuclear Magnetic Resonance Spectroscopic Approaches for the Determination of friterglycosidic Linkage and Sequence in Oligosaccharides. Phytochem Anal 7 113... 

Structure A was chosen to have (p ip values near those for the single minimum energy structure determined for globoside using Bock and Lemiuex s HSEA program (39,40). Structure B was chosen because it also has

previous studies of oligosaccharide conformation. Structure C was chosen to have ip values displaced 120° from the other initial structures. 

Jakob CA, Burda P, Roth J, Aebi M (1998) Degradation of misfolded endoplasmic reticulum glycoproteins in Saccharomyces cerevisiae is determined by a specific oligosaccharide structure. J Cell Biol 142 1223-1233 Janson LW, Ragsdale K, Luby-Phelps K (1996) Mechanism and size cutoff for steric exclusion from actin-rich cytoplasmic domains. Biophys ) 71 1228-1234 Jeffers M, Taylor GA, Weidner KM, Omura S, Vande Woude GF (1997) Degradation of the Met tyrosine kinase receptor by the ubiquitin-proteasome pathway. Mol Cell Biol 17 799-808... 

The pairwise additivity principle when applied to bichromophoric exciton-coupled systems, such as those composed of 4-bromobenzoate (BB) and 4-methoxycinnamate (MC) derivatives of cyclic polyols, yields more information from the CD spectra of complex molecules173. In such systems both degenerate ( homo") interactions, i.e., BB/BB and MC/MC, and nondegenerate ("hetero") interactions, i.e., BB/MC, contribute to the exciton CD spectra. As the homo exciton Cotton effects arc well separated (BB 236/253 nm, MC 287/322 nm) a unique pattern of CD curves is obtained for each derivative of cyclic tri- or tetraol. This method is particularly useful in identification of glycopyranosides174, a procedure essential for microscale structure determination of oligosaccharides by the exciton chirality method175. 

Excellent survey of the uses of NMR, mass spectrometry, and enzymatic reagents to determine oligosaccharide structure. 

Subsequent investigations on the structure of heparin concentrated on the isolation and structural determination of larger oligosaccharides, in order to determine the structural elements involved in anti-blood-clotting activity associated with the binding to antithrombin. 

It thus became desirable to understand, first, the basis of this determinism in the creation of glycosidic linkages, and second, the order in which the residues of monosaccharides of the branching points are conjugated. Some work has now been performed that demonstrates that this double problem is linked simultaneously to the specificity of the glycosyltransferases and to the presence of well defined, oligosaccharide structures in the glycan molecule. For example, Roseman s... 

Nonetheless, there is one macromolecule — the Fc fragment of the human IgGj Immunoglobulin — with a complex carbohydrate structure attached to it which allowed the determination of the decasaceharide conformation down to atomic resolution [37, 38] (cf. below). Another system which allowed the resolution of the oligosaccharide structure is the rabbit IgGx Fc-fragment [39]. 

K. Nakanishi Microscale structure determination of oligosaccharides a chirooptical method... 

---