Crystal structure and hydrogen bonding system in cellulose 1α, from synchrotron X-ray and neutron fiber diffraction
Crystal structure and hydrogen bonding system in cellulose 1α, from synchrotron X-ray and neutron fiber diffraction
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DOI：
10.1021/ja037055w
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发表时间：
2003-11-26
影响因子：
15
通讯作者：
Langan, P
中科院分区：
文献类型：
--
作者：
Nishiyama, Y;Sugiyama, J;Langan, P
的晶体和分子结构，连同氢键系统中的纤维素I-α已被确定使用原子分辨率同步辐射和中子衍射数据记录定向纤维样品通过对齐纤维素微晶从细胞壁的淡水藻Glaucocystis nostochinearum。X射线数据用于确定C和O原子的位置。所得结构是单链三斜晶胞，其中所有葡糖基键和羟甲基（tg）相同。然而，相邻的糖环在构象上交替，使链具有纤维二糖基重复。这些链以“平行向上”的方式组织成片状。使用从氢化和氘化样品中收集的中子衍射数据，通过傅里叶差分分析确定参与氢键合的氢原子的位置。本文报道的纤维素I-α和先前报道的纤维素I-β的结构和氢键之间的差异为I-α-> I-β的固态转化和天然纤维素中两种晶相的出现提供了潜在的解释。
The crystal and molecular structure, together with the hydrogen-bonding system in cellulose I-alpha has been determined using atomic-resolution synchrotron and neutron diffraction data recorded from oriented fibrous samples prepared by aligning cellulose microcrystals from the cell wall of the freshwater alga Glaucocystis nostochinearum. The X-ray data were used to determine the C and O atom positions. The resulting structure is a one-chain triclinic unit cell with all glucosyl linkages and hydroxymethyl groups (tg) identical. However, adjacent sugar rings alternate in conformation giving the chain a cellobiosyl repeat. The chains organize in sheets packed in a "parallel-up" fashion. The positions of hydrogen atoms involved in hydrogen-bonding were determined from a Fourier-difference analysis using neutron diffraction data collected from hydrogenated and deuterated samples. The differences between the structure and hydrogen-bonding reported here for cellulose I-alpha and previously for cellulose I-beta provide potential explanations for the solid-state conversion of I-alpha --> I-beta and for the occurrence of two crystal phases in naturally occurring cellulose.