Atomic resolution of cotton cellulose structure enabled by dynamic nuclear polarization solid-state NMR
Atomic resolution of cotton cellulose structure enabled by dynamic nuclear polarization solid-state NMR
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DOI：
10.1007/s10570-018-2095-6
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发表时间：
2019-01-01
期刊：
影响因子：
5.7
通讯作者：
Wang, Tuo
中科院分区：
文献类型：
--
作者：
Kirui, Alex;Ling, Zhe;Wang, Tuo
传统方法的分辨率不足长期以来限制了对纤维素及其衍生物的结构解释，特别是对于结晶度相对较低的或天然细胞壁中的纤维素及其衍生物。最近对C-13均匀标记的植物生物材料的2D/3D固体核磁共振研究引发了我们对纤维素结构及其与基质聚合物相互作用的现有知识的重新调查，但对于未标记的材料，由于灵敏度的限制，这种光谱方法变得不实用。在这里，我们结合自然丰度的C-13-C-13二维相关固态核磁共振波谱，结合动态核极化的灵敏度增强技术，以及对观察到的和文献报道的化学位移的统计分析，来研究未标记的棉花纤维素的分子结构。原子分辨率使我们能够监测在球磨过程中I和I同素的损失和新结构的产生，这揭示了大的微晶尺寸对于保持I和I模型结构的重要性。在“无序”的区域中已经确定了偏序，这是由良好分辨的峰的离散分布所证明的。这项研究不仅提供了迄今为止无法获得的对棉花纤维素的高分辨率见解，而且为分析富含纤维素的材料的结构提供了一种广泛适用的策略，而不需要进行同位素标记。这项工作是同一期上一篇文章中描述的球磨棉花多技术研究的一部分。
The insufficient resolution of conventional methods has long limited the structural elucidation of cellulose and its derivatives, especially for those with relatively low crystallinities or in native cell walls. Recent 2D/3D solid-state NMR studies of C-13 uniformly labeled plant biomaterials have initiated a re-investigation of our existing knowledge in cellulose structure and its interactions with matrix polymers but for unlabeled materials, this spectroscopic method becomes impractical due to limitations in sensitivity. Here, we investigate the molecular structure of unlabeled cotton cellulose by combining natural abundance C-13-C-13 2D correlation solid-state NMR spectroscopy, as enabled by the sensitivity-enhancing technique of dynamic nuclear polarization, with statistical analysis of the observed and literature-reported chemical shifts. The atomic resolution allows us to monitor the loss of I and I allomorphs and the generation of a novel structure during ball-milling, which reveals the importance of large crystallite size for maintaining the I and I model structures. Partial order has been identified in the "disordered" domains, as evidenced by a discrete distribution of well-resolved peaks. This study not only provides heretofore unavailable high-resolution insights into cotton cellulose but also presents a widely applicable strategy for analyzing the structure of cellulose-rich materials without isotope-labeling. This work was part of a multi-technique study of ball-milled cotton described in the previous article in the same issue.