Li Jingyuan, Gong Xiaojing, Lu Hangjun, Li Ding, Fang Haiping, Zhou Ruhong
Department of Physics, Zhejiang University, Hangzhou 310027, China.
Proc Natl Acad Sci U S A. 2007 Mar 6;104(10):3687-92. doi: 10.1073/pnas.0604541104. Epub 2007 Feb 27.
Water permeation across a single-walled carbon nanotube (SWNT) under the influence of a mobile external charge has been studied with molecular dynamics simulations. This designed nanopore shows an excellent on-off gating behavior by a single external charge (of value +1.0e): it is both sensitive to the available charge signal when it is close (less than a critical distance of 0.85 A or about half the size of a water molecule) and effectively resistant to charge noise, i.e., the effect on the flow and net flux across the channel is found to be negligible when the charge is >0.85 A away from the wall of the nanopore. This critical distance can be estimated from the interaction balance for the water molecule in the SWNT closest to the imposed charge with its neighboring water molecules and with the charge. The flow and net flux decay exponentially with respect to the difference between these two interaction energies when the charge gets closer to the wall of the SWNT and reaches a very small value once the charge crosses the wall, suggesting a dominating effect on the permeation properties from local water molecules near the external charge. These findings might have biological implications because membrane water channels share a similar single-file water chain inside these nanoscale channels.
利用分子动力学模拟研究了在移动外部电荷影响下，水通过单壁碳纳米管（SWNT）的渗透情况。这种设计的纳米孔通过单个外部电荷（值为+1.0e）表现出优异的开关门控行为：当外部电荷靠近时（小于0.85埃的临界距离或约为水分子大小的一半），它对可用电荷信号敏感，而当电荷距离纳米孔壁大于0.85埃时，它对电荷噪声具有有效抗性，即发现电荷噪声对通过通道的水流和净通量的影响可忽略不计。这个临界距离可以根据单壁碳纳米管中最靠近施加电荷的水分子与其相邻水分子以及电荷之间的相互作用平衡来估算。当电荷靠近单壁碳纳米管的壁时，水流和净通量相对于这两种相互作用能之间的差值呈指数衰减，并且一旦电荷穿过管壁，水流和净通量就会达到非常小的值，这表明外部电荷附近的局部水分子对渗透特性具有主导作用。这些发现可能具有生物学意义，因为膜水通道在这些纳米级通道内共享类似的单列水链。
