Figure 3.

Gel-permeation chromatography showing the molecular mass distribution of native maize β-glucan compared with β-glucan synthesized in vitro at various low substrate concentrations. The native β-glucan and the products of the in vitro reactions were dissolved in McIlvaine's buffer, pH 5.5, and loaded onto a 2.5- × 40-cm column of Sepharose 4B equilibrated in the same buffer. Four-milliliter fractions were collected, and a portion was digested with the B. subtilis endoglucanase enzyme for HPAE-HPLC. The β-glucan was detected either by total sugar (Dubois et al., 1956) or by radioactivity as assayed by liquid scintillation spectroscopy. The distribution of native β-glucan observed here was essentially identical for β-glucans extracted from excised coleoptile sections incubated with labeled Glc as described in Tables II and III. Two experiments were run with essentially identical results. Fractions from in vivo labeling experiments were pooled (designated I, II, III, and Incl. [included]), dialyzed against deionized water, and assayed for cellodextrin distribution in β-glucan as described in Table III. Peak fractions of dextran standards for molecular mass (in kD) are marked.