Propeties of Native Cellulose II with Folded-Chain Structure

(1)建立了天然产带菌株的培养条件。散装材料给出了明确定义的纤维素II的X射线衍射图。(2)天然带状纤维素的酸水解稳定性与其它纤维素相似，但其稳定值（LODP）（18.4）明显低于其它纤维素。当天然带状纤维素溶解并从浓碱中再生时，其特征带形态丧失，LODP变为约50，其值与普通再生纤维素相似。这些结果有力地支持了所提出的模型，定期链折叠的天然带的周期为10 nm。(3)本机带的典型厚度由阴影技术确定为约。10 nm。(4)对天然谱带酸水解后的固体~（13）C NMR谱的变化分析表明，链折叠区含有葡萄糖残基的不规则构象，其对谱图的贡献与其它纤维素的无定形区一致。(5)这些发现导致一个模型的天然带状纤维素组成的股样结构，每个组成的约。16葡聚糖链形成一个单分子片，随后定期折叠。

(1) Culture conditions for the native band-producing strain were established. The bulk material gave the X-ray diffraction pattern of well defined cellulose II.(2) Leveling-off behavior on acid hydrolysis of native band cellulose was similar to those of other cellulose samples, but the former's leveling-off value (LODP) (18.4) was remarkably lower than others. When the native band cellulose was dissolved in and regenerated from concentrated alkali, its cahracteristic band morphology was lost and LODP changed to ca.50, a value similar to ordinary regenerated celluloses. These results strongly support the proposed model of regular chain folding in the native band with a periodicity of 10 nm.(3) The typical thickness of native band was determined by shadowing technique as ca.10 nm.(4) Analysis of the change in solid-state 13C NMR spectrum by acid hydrolysis of native band showed that the chain folding region involved irregular conformations of glucose residues, whose contribution to the spectrum coinciding with that of amorphous regions of other celluloses.(5) These findings lead to a model of native band cellulose consisting of strand-like structures each composed of ca.16 glucan chains forming a monomolecular sheet, which is subsequently folded regularly.