Synthesis of Cellulose and Its Formation Mechanism

用透射电子显微镜直接观察合成纤维素酶催化的β-纤维二糖氟化物单体在乙腈-缓冲溶剂体系中合成纤维素酶的形成过程。聚合反应开始后30秒即可观察到合成纤维素。反应初期发生胶束相分离。在胶束粒子的边界处形成了不规则的纤维素聚集体，表明该界面是聚合的场所。用热表面活性剂溶液处理后的纤维素产品被强烈标记为纤维二糖水解酶-金粒子，表明所生成的聚合物为纤维素。产物的电子衍射谱显示出典型的纤维素II的晶体结构。在优化的乙腈/醋酸酯缓冲体系中，通过纤维素酶催化底物单体的聚合，首次在体外合成了具有天然纤维素I电子衍射谱特征的纤维素微纤维。绿色木霉纤维素酶的部分纯化是合成纤维素I异构体所必需的。合成纤维素I的组装似乎是部分纯化的酶与底物在有机/水溶剂体系中胶束聚集的结果，有利于具有相同极性的葡聚糖链的排列和延伸链的构象，导致结晶形成亚稳定的纤维素I异构体。

Direct Visualization of Synthetic Cellulose Formation by Transmission Electron MicroscopyThe process of synthetic cellulose formation in an acetonitrile-buffer solvent system by enzymatic polymerization of beta-cellobiosyl fluoride monomer using cellulase as catalyst was visualized by transmission electron microscopy. Synthetic cellulose could be observed as soon as 30 sec after initiation of the polymerization. A micellar phase separation occurred at the initial stage of the reaction. Irregular aggregates of cellulose were formed at the boundary of the micellar particle, suggesting that the interface is the site of polymerization. The cellulose product after treatment with hot surfactant solution was strongly labeled with cellobiohydrolase-gold particles, indicating that the produced polymer is cellulose. The electron diffraction pattern of the product showed the typical pattern of crystal structure of cellulose II.The First In Vitro Synthesis of Cellulose ICellullose microfibrils with an electron diffraction pattern characteristic of native cellulose I have been synthesized abiotically via a cellulase-catalyzed polymerization of beta-cellobiosyl fluoride substrate monomer in an optimized acetonitrile/acetate buffer system. Partial purification of the Trichoderma viride cellulase enzyme was found essential for the formation of the synthetic cellulose I allomorph. Assembly of synthetic cellulose I appears to be a result of a micellar aggregation of the partially purified enzyme and the substrate in an organic/aqueous solvent system, favoring the alignment of glucan chains with the same polarity and extended chain conformation resulting in the crystallization to form the metastable cellulose I allomorph.