The chemical structures of inulins, levans, highly branched fructans. and fructan oligomers from plants were determined by gas-liquid chromatography of partially methylated alditol acetates and "C nuclear magnetic resonance spectroscopy of the native polymers. Results obtained by these sensitive techniques revealed that these polymers contained small proportions of linkages atypical of the expected structures; inulins were composed of primarily (2+ l)-linked p-o-fructofuranosyl units, but contained measurable amounts of(2+ 1,2-6)-linked branch point residues and (_ T-+6)-linked fructosyl units. and the levans possessed atypical (2+ I )-linked fructofuranosyl and branch-point residues. The highly branched wheat fructans were particularly dynamic, exhibiting enrichment of (2 -+ I)-linkages during early induction of synthesis but enrichment of (2-6) linkages upon extended periods of fructan accumulation. The techniques used here should prove valuable in determining the biological significance of these variations in structure.
. abundant linkages, were often not sufficiently sensitive to detect small amounts of other linkages that might have been present in the polymer. More recent studies of bacterial levans and plant fructans using "C-n.m.r.'b'o and g.l.c.-m.s. of partly O-methylated alditol acetates"-'3 have demonstrated that these techniques provide sufficient sensitivity to determine both the proportion of(2+ I)-and (2-6)-linkedp-D-fructosyl units and