Fig. 16.

Chemical and enzymatic treatment of an N-glycan modified with a branched fucose residue. The RP-HPLC glycan fraction of 12 g.u. (see Fig. 13) was treated with hydrofluoric acid (B) and then further incubated with the branch-specific honeybee FDL β-hexosaminidase (C) prior to positive-ion mode MALDI-TOF MS. Alterations in the structure were also monitored by MS/MS (see insets for the nondigested and digested forms). About 40% of the antennal modification was removed by hydrofluoric acid (a percentage consistent with α1,4-fucosylation) to yield a nonreducing terminal GlcNAc, which is concluded to be on the α1,3-arm due to its sensitivity toward the FDL β-hexosaminidase.