The α-d-glucopyranosidic linkages of dextrans: comparison of percentages from structural analysis by periodate oxidation and by methylation

The analyses of 25 dextrans by g.l.c.-m.s., methylation-fragmentation, and periodate-oxidation techniques have been compared. Although in general agreement for slightly branched dextrans, the two techniques yield divergent analyses for highly branched dextrans. Employing the methylation-fragmentation data as the standard, the periodate-oxidation data were examined to establish the extent of deviation for the types of α-d-glucopyranosidic linkages that occur in dextrans, that is, the (1→6)-like, the (1→4)-like, and the (1→3)-like. The unexpected behavior of the dextrans was correlated with whether branching occurs through either C-2 or C-4, or C-3 or both of these types. Possible causes for the effects observed are discussed.