Bergenstråhle Malin, Thormann Esben, Nordgren Niklas, Berglund Lars A
Department of Fibre and Polymer Technology, Royal Institute of Technology, Teknikringen 58, SE-10044 Stockholm, Sweden.
Langmuir. 2009 Apr 21;25(8):4635-42. doi: 10.1021/la803915c.
Pulling single cellulose molecules from a crystalline cellulose surface has been modeled by molecular dynamics (MD) simulations of the experimental procedure used in atomic force microscopy (AFM). Specifically, the aim of the study was to investigate cellulose interactions at desorption. Simulations were performed in both water and the organic solvent cyclohexane. Moreover, the effects of initial octamer conformation and orientation with respect to the surface chains were studied. A strong effect from the solvent was observed. In cyclohexane, normal forces of 200-500 pN and energies of 43.5+/-6.0 kJ/mol glucose unit were required to pull off the octamer. The normal forces in water were substantially lower, around 58 pN, and the energies were 18.2+/-3.6 kJ/mol glucose unit. In addition, the lateral components of the pull-off force were shown to provide information on initial conformation and orientation. Hydrogen bonds between the octamer and surface were analyzed and found to be an important factor in the pull-off behavior. Altogether, it was shown that MD provides detailed information on the desorption processes that may be useful for the interpretation of AFM experiments.
通过对原子力显微镜（AFM）实验过程进行分子动力学（MD）模拟，对从结晶纤维素表面拉出单个纤维素分子的过程进行了建模。具体而言，该研究的目的是研究纤维素在解吸过程中的相互作用。在水和有机溶剂环己烷中都进行了模拟。此外，还研究了初始八聚体构象和相对于表面链的取向的影响。观察到溶剂有很强的影响。在环己烷中，拉出八聚体需要200 - 500 pN的法向力和43.5±6.0 kJ/mol葡萄糖单元的能量。水中的法向力要低得多，约为58 pN，能量为18.2±3.6 kJ/mol葡萄糖单元。此外，解拉力的横向分量显示出能提供有关初始构象和取向的信息。对八聚体与表面之间的氢键进行了分析，发现这是解吸行为中的一个重要因素。总的来说，结果表明分子动力学为解吸过程提供了详细信息，这可能有助于解释原子力显微镜实验。
