Conformational analysis of some mannose‐containing and milk oligosaccharides: Correlation of their shape with inhibitory properties in antigen/antibody interactions

Abstract

AbstractPossible conformations of two mannotetraoses and several milk oligosaccharides have been studied by an energy minimization procedure using semi‐empirical potential functions. Changes in the terminal residue at the reducing end (cyclic to acyclic form) of these molecules do not affect the favored conformations of the remaining oligosaccharide moiety. However, differences in the overall shape of the native and reduced forms of the mannotetraose, mannose α(1–3) mannose α(1–2) mannose α(1–2) mannose are much less marked than between the native and reduced forms of lacto‐N‐tetraose. These differences are related to the effectiveness of the native forms as inhibitors of antibodies produced using synthetic antigens. Changes in the linkage of the residues at the nonreducing end of these molecules affect significantly the overall shape of these molecules. These differences also are related to their effectiveness as inhibitors. In the fucose‐containing milk oligosaccharides the additional fucose residues only restrict the orientation of the backbone tetrasaccharide and do not push it into a totally new conformation. The fucose residues come on a surface of the molecule which is away from the region which may be important for binding. The present studies show that it is the overall shape of the molecule which is important in determining its inhibitory properties and give information as to how best to use the immune method for identification of unknown oligosaccharide sequences by specially prepared antibodies.