STRUCTURAL STUDIES OF (1-]3),(1-]4)-BETA-D-GLUCANS BY C(13)-NUCLEAR MAGNETIC-RESONANCE SPECTROSCOPY AND BY RAPID ANALYSIS OF CELLULOSE-LIKEREGIONS USING HIGH-PERFORMANCE ANION-EXCHANGE CHROMATOGRAPHY OF OLIGOSACCHARIDES RELEASED BY LICHENASE

The structures of (1 --> 3),(1 --> 4)-beta-D-glucans (beta-glucans) we re evaluated by high-performance anion-exchange chromatography (HPAEC) of the oligosaccharides produced by the action of (1 --> 3),(1 --> 4) -beta-D-glucan-4-glucanohydrolase (lichenase; EC 3.2.1.73). The relati ve amounts of the released oligosaccharides constitute a fingerprint o f structure, and the method is particularly useful for identification of minor, cellulose-like features in the polysaccharides. In general, the cereal beta-glucans were similar, but the ratio of (1 --> 3)-linke d cellotriosyl to (1 --> 3)-linked cellotetraosyl units, which constit uted approximately 90% of the polysaccharides, was lower for oats (2.1 -2.4) than it was for barley and rye (2.8-3.3). A portion (3-4%) of oa t and barley beta-glucan was rendered water-insoluble by lichenase. HP AEC revealed that these products, shown by C-13-nuclear magnetic reson ance spectroscopy to be cellulose-like, were composed of oligosacchari des of degree of polymerization 9-15. Lichenan is distinct from cereal beta-glucans, being mainly (1 --> 3)-linked cellotriosyl units. No ev idence for consecutive (1 --> 3)-linkages was found in any of the beta -glucans. The extractability of oat and barley beta-glucan was not rel ated to identifiable structural differences. Oat aleurone beta-glucan has less of the (1 --> 3)-linked cellotetraosyl units than did endospe rmic beta-glucan.