Structural and conformational analysis of sialyloligosaccharides using carbon-13 nuclear magnetic resonance spectroscopy.
The analysis of the carbon-13 chemical shift data of NeuAc alpha (2----3)Gal beta (1----4)Glc and NeuAc alpha (2----3)Gla beta-(1----4)GlcNAc and their respective NeuAc alpha (2----6) isomers established distinct and different conformations of the sialic acid residue, depending on the type of anomeric linkage [alpha-(2----3) vs. alpha (2----6)]. Interactions between the NeuAc residue and the Glc or GlcNAc residue are particularly strong in the case of the alpha (2----6) isomers. Similar effects are observed for the larger oligosaccharides [II3(NeuAc)2Lac and IV6NeuAcLcOse4] and even in intact glycoproteins and polysaccharides. It is proposed that the NeuAc alpha (2----3) isomers assume an extended conformation with the sialic residue at the end (terminal) of the oligosaccharide chain or branch. The NeuAc alpha (2----6) isomers are assumed to be folded back toward the inner core sugar residues.
D000818:Animals; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002417:Cattle; D003126:Colostrum; D005260:Female; D006801:Humans; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008895:Milk, Human; D009844:Oligosaccharides; D011247:Pregnancy; D013329:Structure-Activity Relationship
D009844:Oligosaccharides; C016735:sialooligosaccharides