Different Conformations of Surface Cellulose Molecules in Native Cellulose Microfibrils Revealed by Layer-by-Layer Peeling
Different Conformations of Surface Cellulose Molecules in Native Cellulose Microfibrils Revealed by Layer-by-Layer Peeling
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DOI：
10.1021/acs.biomac.7b01173
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发表时间：
2017-11-01
影响因子：
6.2
通讯作者：
Isogai, Akira
中科院分区：
文献类型：
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作者：
Funahashi, Ryunosuke;Okita, Yusuke;Isogai, Akira
采用2，2，6，6-四甲基哌啶-1-氧基自由基氧化-热碱抽提的重复顺序工艺，实现了天然纤维素微纤维表面分子的逐层剥离。研究了高结晶度的藻类和被囊类纤维素以及低结晶度的棉纤维和木材纤维。最初，面向外部的每个藻类纤维素微原纤维最外表面分子的C6-羟基具有guche-guche(GG)构象，而面向内部的微纤维分子的c6-羟基具有guche-trans(GT)构象。形成结晶纤维I的纤维素分子中的其他C6-羟基均为反式高切(Tg)构象。表面剥离后，微原纤维表面原来的第二层分子变为最外表面分子，原来的Tg构象转变为GG和GT构象。植物纤维素微纤维可能具有最外层和第二层分子的无序结构，正如使用相同的逐层剥离技术所展示的那样。
Layer-by-layer peeling of surface molecules of native cellulose microfibrils was performed using a repeated sequential process of 2,2,6,6-tetramethylpiperidine-1-oxyl radical-mediated oxidation followed by hot alkali extraction. Both highly crystalline algal and tunicate celluloses and low crystalline cotton and wood celluloses were investigated. Initially, the C6-hydroxy groups of the outermost surface molecules of each algal cellulose microfibril facing the exterior had the gauche-gauche (gg) conformation, whereas those facing the interior had the gauche-trans (gt) conformation. All the other C6-hydroxy groups of the cellulose molecules inside the microfibrils contributing to crystalline cellulose I had the trans-gauche (tg) conformation. After surface peeling, the originally second-layer molecules from the microfibril surface became the outermost surface molecules, and the original tg conformation changed to gg and gt conformations. The plant cellulose microfibrils likely had disordered structures for both the outermost surface and second-layer molecules, as demonstrated using the same layer-by-layer peeling technique.