DIMERS OF A GFG HEXASACCHARIDE OCCUR IN APPLE FRUIT XYLOGLUCAN

Apple fruit xyloglucan is predominantly built up from XXXG, XXFG, and XLFG units (G = beta-D-Glcp-, X = alpha-D-Xylp-(1 --> 6)-beta-D-Glcp-, L = beta-D-Galp-(1 --> 2)-alpha-D-Xylp-(1 --> 6)-beta-D-Glcp-, F = al pha-L-Fucp-(1 --> 2)-beta-D-Galp-(1 --> 2)-alpha-D-Xylp-(1 --> 6)-beta -D-Glcp-). However, small amounts of oligosaccharides with a less heav ily branched glucan backbone also occur. Structural analysis of two su ch oligosaccharides, isolated from a xyloglucan preparation digested w ith endoglucanase IV, using a combination of FAB mass spectrometry and H-1 NMR spectroscopy, afforded the identification of GFG and a dimer of GFG. The finding of the dodecasaccharide GFGGFG as a structural ele ment of apple fruit xyloglucan is most unusual. (C) 1998 Elsevier Scie nce Ltd.