Dimers of a GFG hexasaccharide occur in apple fruit xyloglucan

Apple fruit xyloglucan is predominantly built up from XXXG, XXFG, and XLFG units (G = β-d-Glcp-, X = α-d-Xylp-(1 → 6)-β-d-Glcp-, L = β-d-Galp-(1 → 2)-α-d-Xylp-(1 → 6)-β-d-Glcp-, F = α-l-Fucp-(1 → 2)-β-d-Galp-(1 → 2)-α-d-Xylp-(1 → 6)-β-d-Glcp-). However, small amounts of oligosaccharides with a less heavily branched glucan backbone also occur. Structural analysis of two such oligosaccharides, isolated from a xyloglucan preparation digested with endoglucanase IV, using a combination of FAB mass spectrometry and 1H NMR spectroscopy, afforded the identification of GFG and a dimer of GFG. The finding of the dodecasaccharide GFGGFG as a structural element of apple fruit xyloglucan is most unusual. Two fragments, isolated from an endoglucanase IV digest of apple fruit xyloglucan, were identified as GFG and a dimer of GFG (GFGGFG). The finding of the dodecasaccharide is most unusual. GFGGFG α-l-Fuc p-(1 → 2)-β-d-Gal p-(1 → 2)-α-d-Xyl p-(1 → 6)-β-d-Glc p-(1 → 4)-β-d-Glc p-(1 → 4)-β-d-Glc p-(1 → 4)-β-d-Glc p-(1 → 4)-β-d-Glc p-(1 → 4)-d-Glc p-α-l-Fuc p-(1 → 2)-β-d-Gal p-(1 → 2)-α-d-Xyl p-(1 → 6)