The interaction between cellulose microfibrils and xylan is crucial for the strength of the secondary cell wall of vascular plants. In this paper, molecular dynamics simulations are used to study the adsorption of xylan on both the hydrophilic (110) and hydrophobic (200) planes of cellulose microfibers and the conformational adaptation of xylan on the plane. The simulation results show that the cellulose and xylan chains are more stable in parallel mode in both planes. The xylan orientation prefers to be parallel with the cellulose microfibrils in the presence of water molecules. The adsorption of xylan on the (110) plane of cellulose microfibrils is dominated by electrostatic interactions, while on the (200) plane, it is dominated by dispersion interactions. The adsorption on hydrophilic planes is superior to that on hydrophobic planes. Meanwhile, a novel independent gradient model is applied to the analysis of weak intermolecular interactions. In addition, a few xylans can adopt a two-fold helical conformation on the (200) plane of cellulose microfibrils. The dominant conformation of xylan in other cases remains the three-fold helix. Xylan is more easily converted to the two-fold helical conformation on the (200) plane than on the (110) plane. The addition of water molecules will reduce the stability of the two-fold helical conformation of xylan.

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分子动力学模拟对纤维素微纤维和半纤维素之间相互作用的见解

纤维素微纤维和木聚糖之间的相互作用对于维管植物次生细胞壁的强度至关重要。在本文中，分子动力学模拟用于研究木聚糖在纤维素微纤维的亲水（110）和疏水（200）平面上的吸附以及木聚糖在平面上的构象适应。模拟结果表明，纤维素和木聚糖链在两个平面上以平行模式更加稳定。在水分子存在的情况下，木聚糖取向更倾向于与纤维素微纤丝平行。木聚糖在纤维素微纤丝的(110)面上的吸附主要由静电作用，而在(200)面上的吸附作用主要是分散作用。在亲水平面上的吸附优于在疏水平面上的吸附。同时，一种新颖的独立梯度模型被应用于弱分子间相互作用的分析。此外，少数木聚糖可以在纤维素微纤维的（200）平面上采用双螺旋构象。在其他情况下，木聚糖的主要构象仍然是三重螺旋。木聚糖在 (200) 平面上比在 (110) 平面上更容易转化为双螺旋构象。水分子的加入会降低木聚糖双螺旋构象的稳定性。木聚糖在 (200) 平面上比在 (110) 平面上更容易转化为双螺旋构象。水分子的加入会降低木聚糖双螺旋构象的稳定性。木聚糖在 (200) 平面上比在 (110) 平面上更容易转化为双螺旋构象。水分子的加入会降低木聚糖双螺旋构象的稳定性。