Structural features of water soluble (1,3)(1,4)-beta-D-glucans from high-beta-glucan and traditional oat lines

摘要

Information on structural features of beta-glucans purified from a traditional (4.4% beta-glucan) and two high beta-glucan oat lines (6.0 and 7.3%) was obtained by partial and complete hydrolysis with lichenase.The depolymerization process was monitored with disodium 2,2'-bicinchoninate reductometry (BCA),fluorophore-assisted capillary-electrophoresis (FACE)and nuclear-magnetic-resonance spectroscopy (NMR).The average degree of polymerization (DP)of the completely hydrolyzed beta-glucans was the same for beta-glucans from te three oat lines,as determined from NMR spectra (3.7),by FACE (3.4),and by BCA (3.9).By FACE,the beta-glucans from all three lines had the same molar ratio of cellobiosyl-(1,3)-D-glucose/cellotriosyl-(1,3)-D-glucose units of 1.6.By NMR the ratio of beta (1,4)/beta(1,3) before hydrolysis was 2.4 and after complete hydrolysis 1.7,with no significant differences among oat lines.Identical molar ratios of penultimate oligosaccharides (DP6,DP7 and DP8)released during partial depolymerization suggested the same arrangement of cellotriosyl/cellotetraosyl residues in the beta-glucan polymers from normal and high beta-glucan oat lines.Differences in lichenase specificity toward the beta-glucans from the three sources,however,were observed during partial depolymerization,which were attributed to differences in chain lengths of the three polymers.The preferred substrate was the polymer with the highest initial DP.A more limited specificity was observed for the beta-glucans with the lowest initial DP.