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We have reviewed our previous 13C NMR studies on conformational elucidation of various types of polysaccharides in the solid state based on conformation-dependent displacement of 13C chemical shifts. In general, it was shown that polymorphs of crystalline polysaccharides are readily distinguished by examination of 13C NMR spectra. Further, it is interesting to note that many kinds of polysaccaharides adopt distinct conformations as examined by 13C NMR, although they are amorphous as viewed from X-ray diffraction. In particular, we showed that three conformations, single chain, single helix, and triple helix, are present for (1→3) -β-D-glucans and -xylans of high molecular weight, depending on origin and physical treatment. It turned out that the presence of the single helix is responsible for gelation of resilient gel, antitumor activity, and activation of factor G in lymulus amebocyte lysate, although gel network of branched glucans is formed by partial association of triple-helical chains. We further studied 13C NMR studies of amylose and agarose to gain insight into gelation mechanism of these systems. |
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