Urea-Induced Drying of Hydrophobic Nanotubes: Comparison of Different Urea Models

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• 作者：Peng Xiu ; Zaixing Yang ; Bo Zhou ; Payel Das ; Haiping Fang ; Ruhong Zhou
• 刊名：Journal of Physical Chemistry B
• 出版年：2011
• 出版时间：March 31, 2011
• 年：2011
• 卷：115
• 期：12
• 页码：2988-2994
• 全文大小：1031K
• 年卷期：v.115,no.12(March 31, 2011)
• ISSN：1520-5207

文摘

In a previous study, we performed the molecular dynamics (MD) simulations of various carbon nanotubes solvated in 8 M urea and observed a striking phenomenon of urea-induced drying of hydrophobic nanotubes, which resulted from the stronger dispersion interaction of urea than water with nanotube (Das, P.; Zhou, R. H. J. Phys. Chem. B2010, 114, 5427鈭?430). In this paper, we have compared five different urea models to investigate if the above phenomenon is sensitive to the urea models used. We demonstrate through MD simulations that the drying phenomenon and its physical mechanism are qualitatively independent of the urea models. Consistent with our previous study, our current analyses with both interaction potential energy and association free energy indicate that there is a 鈥渄ry state鈥?inside the carbon nanotubes, which is caused by the urea鈥檚 preferential binding to nanotubes through stronger dispersion interactions. These results also have implications for understanding the urea-induced protein denaturation by providing further evidence of the potential existence of a 鈥渄ry globule鈥?like transient state during protein unfolding and the 鈥渄irect interaction mechanism鈥?(whereby urea attacks protein directly, rather than disrupts water structure as a 鈥渨ater breaker鈥?. In addition, our study highlights the crucial role of dispersion interaction in the selective absorption of molecules in hydrophobic nanopores and may have significance for nanoscience and nanotechnology.