Oligosaccharides repeating unit

For polysaccharides composed of oligosaccharide repeating units, the structural studies may ultimately lead to a complete structure. Other polysaccharides have less-ordered structures, and the aim of the structural studies should be to define the factors governing these structures. Polysaccharide methodology has been summarized2 in two review articles. 

In the polymers of groups (1) and (2), polysaccharide chains composed of oligosaccharide repeating-units (sometimes, partially modified) are usually linked to a unique oligosaccharide unit present near the point of attachment of the chain to another polymeric chain, or to a lipid anchor. This unit is called the linkage region in the polymers of bacterial cell-wall, and the core region in lipopolysaccharides. 

To clarify the scope and the limitations of this approach, it was first of all necessary to ascertain whether precursors having modified monosaccharide residues may be accepted as substrates by the enzymes responsible both for assembly of the oligosaccharide repeating-units of the polymers and for their polymerization. 

Extension of a polymeric chain through sequential addition of oligosaccharide repeating units (stepwise synthesis). 

The synthesis of the j>. newington O-antigenic polysaccharide by the chemical polymerization pathway will be discussed as an example (J 6 J 7) The first and the most difficult task consists in the preparation of the monomer itself, i. e. , the properly functionalized, oligosaccharide repeating unit. The most usual approach is to introduce the required functions into the already-existing oligosaccharide molecule. 

N. K. Kochetkov, in L. Anderson and F. M. Unger (Eds.), Synthesis of O-antigenic polysaccharides. Pathways for the polymerization of oligosaccharide repeating units, Bacterial Lipopolysaccharides Structure, Synthesis and Biological Activities, ACS Symp. Ser., Vol. 231, Amer. Chem. Soc., New York, 1983, pp. 65-81. 

List of oligosaccharide repeating units resuiting from bacteriophage hydroiysis (modified from Sutherland, Highiighted iinkages represent anti-adhesive sequences... 

Phosphoglycan Hydrophilic phosphoglycan consisting of capped oligosaccharide repeat units but minus the GPI anchor and the glycan core 69... 

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