Figure 5.

HPAEC fractionation profiles of known AXO standards and ¹⁴C-radiolabeled oligosaccharides. A, AXO standards were prepared by digestion of wheat AXs with endo-xylanase III as described in “Materials and Methods.” B, Schematic representation of the structures of these AXO standards (• represents Xylp and ⋄ represents Araf residues) as determined by Kormelink et al. (1993a). The AXO standards are numbered from 1 to 12 in A and B. C, Typical fractionation profiles of ¹⁴C-labeled oligosaccharides released from [¹⁴C]Xyl-labeled product 4 (○) and [¹⁴C]GlcA-labeled product 4 (□; see Table II) by treatment with endo-xylanase III. The ¹⁴C-radiolabel was monitored each minute at 30°C and eluted as three peaks around 21 min (peak I), around 23 min (peak II), and around 47 min (peak III). The CarboPac PA10 column was eluted at a rate of 1 mL min⁻¹ with 0.1 m NaOH containing a gradient (0–0.5 m) of sodium acetate for 60 min and then eluted isocratically for 5 min with 1 m sodium acetate. RTs of Xyl, xylobiose, xylotriose, and xylotetraose are indicated as X1, X2, X3, and X4, respectively, in A. PAD, pulsed amperometric detection of carbohydrates using an electrochemical detector (ED50; Dionex). [See online article for color version of this figure.]