Carbohydrate chain structure determination

The data presented here demonstrate that lectins may be used to explore structural aspects of the carbohydrate moieties of specific cell surface bound antigens. Furthermore, it is suggested that the H-2D antigen possesses differences in the structure of the carbohydrate moieties which may reflect microheterogeneity due to the biosynthesis of only partial structures, differences in the number of sialic acid residues, the relationship of the carbohydrate chains to the specific antigenic determinants and/or major structural differences of the carbohydrate chains on different H—2D antigens. 

Over the years, several strategies have been developed for determination of the structure of carbohydrate chains for concise reviews, see Refs. 3 and 4. In particular, the refinements of methylation analysis,15,53 and chemical6-8 and enzymic degradation methods9-10 have permitted... 

Fig. 9. Proposed composite structure showing the relationship of the A, B, H, Le , and Le antigenic determinants of the water-soluble human blood group substances from ovarian cysts. The structure of the side chain in brackets has not been established, but the existence of such a chain is indicated by the mechanism of alkaline borohydride degradation and the oligosaccharides isolated. The carbohydrate chain shown is one of many linked to the serines and threonines of the polypeptide backbone. Chains are not homogeneous and may be of various lengths depending upon genetic composition, incomplete biosynthesis, and unknown factors. From Pereira and Kabat, modified from Lloyd and Kabat cf. Kabat. ...

For glycoproteins, the carbohydrate content (neutral sugars, amino sugars, and sialic acids) is determined. In addition, the structure of the carbohydrate chains, the oligosaccharide pattern (antennary profile), and the glycosylation site(s) of the polypeptide chain are analyzed, to the extent possible. 

No complete structure has been determined for this type of O-linked oligosaccharide in Dictyostelium. These carbohydrate chains are resistant to 3-elimination, suggesting that they are not the standard type of HexNAco/pThr/Ser linkage. This type of modification has been defined by a panel of monoclonal antibodies. Reactivity to this antibody is lost in a series of mutant strains which are collectively said to be mutated at the modB locus. 

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