Spontaneous rearrangement of acetylated xylan on hydrophilic cellulose surfaces
Spontaneous rearrangement of acetylated xylan on hydrophilic cellulose surfaces
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DOI：
10.1007/s10570-021-03706-z
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发表时间：
2021-02-25
期刊：
影响因子：
5.7
通讯作者：
Petridis, Loukas
中科院分区：
文献类型：
--
作者：
Gupta, Madhulika;Rawal, Takat B.;Petridis, Loukas
木聚糖（一种丰富的植物多糖）与纤维素微纤维的相互作用对于次生细胞壁的强度至关重要。更深入地了解这些相互作用对于提高我们对植物细胞壁结构的理解以及设计替代策略来克服纤维素顽抗性以生产生物燃料和可持续生物材料至关重要。木聚糖上天然存在的乙酸盐或葡萄糖醛酸取代已被证明会影响木聚糖-纤维素相互作用。在这里，我们使用无限制的分子动力学模拟来确定四种不同木聚糖与纤维素纤维的 (110) 亲水面的相互作用。在没有纤维素的情况下，无论取代模式如何，所有木聚糖都采用高度灵活的三重螺旋构象。然而，当木聚糖在空间上靠近纤维素表面时，1,2 连接的乙酰基木聚糖 (2AcX) 采用刚性双螺旋构象。 2AcX 构象主要通过乙酰化氧和与纤维素的 C-O6 的糖苷键之间的相互作用来稳定。相反，1,3 连接的乙酰基 (3AcX) 的糖苷氧和乙酰基装饰远离纤维素表面，并且 3AcX 木聚糖在纤维素表面上保持三重螺旋构象。我们的结果表明，木聚糖主链上均匀间隔的化学官能化（带有乙酰基）和取代位置（1,2）在调节木聚糖-纤维素相互作用以稳定纤维素表面上木聚糖的双螺旋构象方面发挥着关键作用。与之前的实验结果进行比较进一步表明，无论取代基的化学性质如何，1,2取代都会在纤维素表面诱导木聚糖的双螺旋构象，而1,3取代主要以三重螺旋构象结合木质素，而不是植物细胞壁中的纤维素。
The interaction of xylan, an abundant plant polysaccharide, with cellulose microfibrils is essential for secondary cell wall strength. A deeper understanding of these interactions is crucial both to improve our understanding of plant cell wall architecture and to design alternate strategies to overcome cellulose recalcitrance for the production of biofuels and sustainable biomaterials. Naturally occurring acetate or glucuronic acid substitutions on xylan have been shown to influence xylan-cellulose interactions. Here, we use unrestrained molecular dynamics simulations to determine the interactions with the (110) hydrophilic face of cellulose fibers of four different xylans. In the absence of cellulose, all xylans, independent of the substitution pattern, adopt a highly flexible threefold helical screw conformation. However, when xylan is spatially close to a cellulose surface 1,2 linked acetyl xylans (2AcX) adopt rigid twofold helical screw conformations. The 2AcX conformations are primarily stabilized by interactions between the acetylated oxygen and the glycosidic linkage with C-O6 of cellulose. In contrast, the glycosidic oxygens and acetyl decorations for 1,3 linked acetyl groups (3AcX) are oriented away from the cellulose surface and the 3AcX xylans maintain threefold helical screw conformations on the cellulose surface. Our results show that evenly spaced chemical functionalization (with acetyl groups) and the position of substitution (1,2) on xylan backbone play key roles in tuning the xylan-cellulose interactions to stabilize the twofold helical screw conformations of xylan on the cellulose surface. A comparison with previous experimental findings further suggests that 1,2 substitutions induce twofold helical screw conformations of xylan on the cellulose surface irrespective of the chemical nature of the substituent, while 1,3 substitutions primarily bind lignin in threefold helical screw conformations rather than cellulose in plant cell walls.