Glucan molecular weight determination

The molecular-weight distribution of a sample of a glucan, pul-lulan, isolated from cultures of the fungus Pullularia pullulans grown in sucrose solutions,"6 was determined by Granath and Kvist69 by the method developed by these workers for use with dextrans. Here, too, the column was calibrated with dextran fractions, as the shape of the pullulan molecule was believed to be sufficiently similar to that of a dextran to permit use of the same correlation of Kav with molecular weight for both polysaccharides. 

Wood, P.J. Beer, M.U. Butler, G. 2000. Evaluation of role of concentration and molecular weight of oat beta-glucan in determining effect of viscosity on plasma glucose and insulin following an oral glucose load. Br. J. Nutr. 84 19-23. 

It provides a direct structural characterization of the in vitro product, as opposed to biochemical techniques that rely on the use of radioactive substrate and a subsequent hydrolysis of the polysaccharides with specific hydrolases. In the case of P-glucans, Hquid C-NMR analysis allows distinction between (1—>3) and (1 4) linkages for products that are soluble in DMSO. For high molecular weight polymers that are insoluble in solvents commonly used for liquid C-NMR analysis, such as cellulose, solid-state NMR spectroscopy can be used for structural characterization. In addition, solid-state NMR spectroscopy provides information on the conformation of the glucan chains in a given preparation as well as structural details that cannot be obtained with Hquid NMR spectroscopy and methylation analysis. For instance, in the case of cellulose, solid-state NMR spectroscopy allows the determination of the proportions of the I and Ip allomorphs in the sample (Atalla and VanderHart 1984). 

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