Schizophyllan triple helix

Figure 6.3 (Top) The chemical structures of schizophyllan, curdlan, and a representative model of schizophyllan triple helix, (a) TEM image of as-grown-SWNT/s-SPG composite, and (b,c) its magnified picture, (d) The original image of (c) was Fourier filtered to enhance the contrast of the composite.41 (Reprinted with permission from M. Numata et al., J. Am. Chem. Soc. 2005, 127, 5875-5884. Copyright 2005 American Chemical Society.)...

It will be evident that theory could be brought into agreement with experiment through arbitrary choice of an equivalent segment equal in length to the persistence of the schizophyllan triple helix. Independent justification for this choice is not apparent, however. 

Fig. (6). Schematic representation of the schizophyllan triple helix. (Hatcheted disks represent the side-chain glucosyl residues, the central cylinder represents the helix core. The disks form a helical chain indicated by the dashed line.). Reproduced from [74] with permission from Elsevier Science.

By applying this method to the triple-stranded helix of schizophyllan (an extracellular (3-, 3-glucan) in water, Yanaki et al. [36] obtained essentially the same values for the above three parameters (Ml = 2150 nm, d = 2.6 nm, and q — 200 nm) from [77] and / measured over a wide range of M. Figure 5-7 shows that their experimental results can be described with these parameter values. This Ml value yields 0.3 nm for /i, which happens to equal the pitch per main chain glucose residue of the schizophyllan triple helix in the crystalline state [37],... 

Fig. 5-7. Molecular weight dependence of [77] and 50 (sedimentation coefficient) for schizophyllan triple helix in water [36]. Curve calculated for an unperturbed wormlike cylinder with q = 200 nm, Ml = 2150 nm, and d = 2.6 nm gives best fits to both [77] and 3o data.

In water, SPG exists as a thermodynamically stable triple-helix (Fig. 2) held together by hydrogen bonds. Under special conditions these hydrogen bonds can be broken for further discussion, it is important to know that, in DMSO, schizophyllan dissociates and exists as a single randomly-coiled chain, but it will re-associate into triple helices upon dilution with water. 

Fig. 2 Structure of schizophyllan repeat unit and a schematic representation of the triple helix formed in aqueous solution. Figure adapted with permission from [45]. 2003 Elsevier...

Fig. 4.24 Molecular structures of p-(l->3)-glucans. The subset (a) shows the repeating unit of schizophyllan, one of the p-(l->3)-glucans, for example. The natural p-(l-43)-glucans take the form of a right-handed triple helix. The subset (b) shows the helix of curdlan the helix pitch and diameter are 1.88 and 1.56 nm, respectively. Here, the circles represent glucoses. The subset (c) shows how the hydrogen bonds are formed between the adjoining glucoses.

We examined whether the other glucans show the same change in the UV or CD spectra when they were treated in the same manner as schizophyllan (i.e., dissolved or dispersed in DMSO and exchanged the solvent for water in the presence of poly(C)). The results shown in Table 4.6 indicate that the complexation is only observed for p-(1 3)-glucans. Although the data are not shown, even when the natural triple helix of schizophyllan was mixed with poly(C), no appreciable change was observed for CD and UV. This shows that the renature process is indispensable for the complexation. 

Since the local polymer conformation in solution is sometimes related to the crystalline structure, the complex structure in solution should be represented by a triple helix similar to that of the original P-(1 3)-glucans. Based on the above discussion, we can construct a structural model for the complex with computer chemistry. First, we constructed the triple helix of schizophyllan (a right-handed 6i triple helix with a 17.4 A) according to the literatures," and took one chain... 

Another y9-(1 3)-D-glucan, named schizophyllan as an antitumor polysaccharide, has been obtained from Schizophylium commune [8,9]. Schizophyllan has similar chemical structure and triple-helix as lentinan [17], as shown in Figure 4. Since Sakurai and Shinkai were the first to find that schizophyllan may form a helical complex with single-stranded homo-polynucleotides [18], many works about preparing a complex of schizophyllan and... 

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