EFFECTS OF EXTERNAL CHARGES ON THE TRANSLOCATION OF SINGLE-FILE WATER MOLECULES

摘要

@@Translocation of water molecules through nanochannels or membrane is of great importance for biological activities as well as for designing novel molecular devices, machines and sensors, which has wide applications in nanotechnology. Structures and thermodynamic properties of single-file water molecules have been paid more and more attentions since the pioneering work of Hummer~1 in 2001. Indeed, in a recent experiment, Holt~2 et al have found that the water flow rate through a carbon nanotube with a radius of 1 to 2 nm was more than three orders of magnitude faster than the conventional hydrodynamic flow. While in a simulation, Joseph and Alum~3 showed that the enhanced flowrate arose from a velocity 'jump' in the depletion region at the water nanotube interface and that the water orientations and hydrogen bonds at the interface significantly affected the flow rate. In this study, we investigate the effects of external charges on the translocation of single-file water molecules through a carbon nanotube. Using molecular dynamics simulations, we found that the water flow was well controlled by an external charge, which is in agreement with a previous study.4 However, we have also found that the net water flux could not be well induced by the "water-pump" model proposed by Gong et al.5 According to Zuo et al6 the pump ability of such a "water-pump" model is very weak, and they appreciate it as a biological water channel rather than a pump, confirmed by our simulations.