A new model for cellulose microfibril

(1)纤维微原纤维的结构和形态：纤维素链呈“平行向上”堆积的单胞结构，其还原末端与c轴重合。因此，在非还原末端合成了纤维素链。纤维素Iβ晶体在一定程度上会发生扭曲，严格地说，它是不完美的晶体。纤维素Iα晶体的表面可能与Iβ晶体的表面不同。天然纤维素的多晶型很可能来自晶体形成阶段的应力或不应力。我们成功地制得了一种高度定向的纤维素微原纤维薄膜。该薄膜的中子衍射表明氢可能在纤维素晶体中的位置。因此，纤维素II晶体是一种反平行堆积，有利于分子的疏水表面。β甲壳素具有平行链堆积，在类似于纤维素I到II的碱处理过程中，通过盐酸溶液的溶胀转变为反平行的α形式。(2)纤维素微纤维的性质-纤维素晶体的热膨胀给出了几点新的认识。晶体只向轴方向膨胀。抗热分解性能取决于纤维微原纤维。我们可以估算出纤维晶体的泊松比。力学现象表明存在一个不稳定的结晶区。木材纵向的杨氏模数表明，非晶态纤维素的取向和密度与晶态纤维素非常相似。对于苎麻纤维，两个方向都存在非晶态部分。(3)纤维素微原纤维对酶的敏感性：纤维素微原纤维对酶的敏感性取决于其形态：Valonia的典型晶体在其表面也有一些缺陷。纤维素微原纤维有其自身的形态。

(1) Structure and morphology of cellulose microfibril :Cellulose chain was found to be in the unit cell with "parallel up" packing, and its reducing end coincides with the c-axis. Consequently, cellulose chain is synthesized on the non-reducing ends. Cellulose I beta crystal distorts some extent and, strictly speaking, it is imperfect crystal. Surface of the cellulose I alpha crystal might be different from that of I beta. It is likely that polymorph of native cellulose comes from with or without stress in the forming stage of the crystal. We succeeded in making a highly oriented film of cellulose microfibril. Neutron diffraction of this film revealed probable position of hydrogen in the cellulose crystal. Consequently, cellulose II crystal is an anti-parallel packing which is favorable to hydrophobic surfaces of the molecule. Beta chitin with parallel chain packing transforms into alpha form of anti-parallel one through swelling by HC1 solution in the similar process of cellulose I to II by alkali treatment.(2) Properties of cellulose microfibrilThermal expansion of cellulose crystal gave several new knowledges. The crystal expands to only aaxis direction. Resistibility of thermal decomposition depends on cellulose microfibril. We can estimate Poison's ratio of the cellulose crystal. Mechanical phenomena suggest an unstable crystalline region. Young's modulus of wood in the longitudinal direction indicates that orientation and density of non-crystalline cellulose is very similar to those of crystalline one. In case of ramie fibers non-crystalline parts exist in the both directions.(3) Susceptibility of cellulose microfibril for enzyme :Susceptibility of cellulose microfibril for enzyme depends on its morphology : Typical crystal of valonia also has some defects on its surface.Cellulose microfibrils have their own morphology coming from their origin.