Crystal structure and hydrogen-bonding system in cellulose 1β from synchrotron X-ray and neutron fiber diffraction
Crystal structure and hydrogen-bonding system in cellulose 1β from synchrotron X-ray and neutron fiber diffraction
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DOI：
10.1021/ja0257319
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发表时间：
2002-08-07
影响因子：
15
通讯作者：
Chanzy, H
中科院分区：
文献类型：
--
作者：
Nishiyama, Y;Langan, P;Chanzy, H
纤维素Ibeta的晶体和分子结构以及氢键系统已被确定使用同步辐射和中子衍射数据记录从定向纤维样品通过对齐纤维素微晶从衣素制备。这些样品衍射了同步加速器X射线和中子，分辨率优于1埃（>300个独特的反射; P2（1））。X射线数据用于确定C和0原子位置，所得结构由两条具有略微不同构象的平行链组成，并以“平行向上”方式排列成片状，所有羟甲基均采用tg构象。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。参与分子内O3的氢原子... O 5氢键具有明确定义的位置，而对应于O2和O 6的那些氢键覆盖更宽的体积，表明具有部分占据的多重几何结构。这种紊乱的观察证实了最近的红外分析，并表明，尽管其高结晶度，纤维素I β晶体具有固有的分子间氢键网络，保持纤维素链在片材的解体。
The crystal and molecular structure together with the hydrogen-bonding system in cellulose Ibeta has been determined using synchrotron and neutron diffraction data recorded from oriented fibrous samples prepared by aligning cellulose microcrystals from tunicin. These samples diffracted both synchrotron X-rays and neutrons to better than 1 Angstrom resolution (>300 unique reflections; P2(1)). The X-ray data were used to determine the C and 0 atom positions, The resulting structure consisted of two parallel chains having slightly different conformations and organized in sheets packed in a "parallel-up" fashion, with all hydroxymethyl groups adopting the tg conformation. 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 hydrogen atoms involved in the intramolecular O3...O5 hydrogen bonds have well-defined positions, whereas those corresponding to 02 and 06 covered a wider volume, indicative of multiple geometry with partial occupation. The observation of this disorder substantiates a recent infrared analysis and indicates that, despite their high crystallinity, crystals of cellulose Ibeta have an inherent disorganization of the intermolecular H-bond network that maintains the cellulose chains in sheets.