title: Water permeation through a charged channel.
abstract: Transport properties of water molecules through hydrophobic channels have been explored extensively in recent years; however, our knowledge about the transport properties of hydrophilic channels is still rather poor. Herein, we use molecular dynamics simulations to study the permeation of water molecules through a charged channel. For comparison, we first consider the pristine hydrophobic channel without charge, and we find an analytic expression that can predict the water flow through it. For uniformly charged channels, with the increase of charge density, the water flow decreases, due to the increase of roughness in the free energy profile experienced by a water molecule along the channel; while the ion flow exhibits a maximum, because of the competition between the increasing ion number and ion-channel attraction. Surprisingly, the water occupancy for positive and negative channels varies in the opposite direction, which is strongly related to the excluded volume effect of ions. Additionally, we also discuss the effect of surface charge patterns and channel sizes. These results not only enrich our understanding of the transport properties of hydrophilic channels, but also have deep implications for the design of nanometer water gates.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Liang
authors.initials: L
authors.lastname: Hao
authors.forename: Jiaye
authors.initials: J
authors.lastname: Su
authors.forename: Hongxia
authors.initials: H
authors.lastname: Guo
mesh_terms: D057927:Hydrophobic and Hydrophilic Interactions; D007477:Ions / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D037742:Nanotubes, Carbon / Q000737:chemistry; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D007477:Ions; D037742:Nanotubes, Carbon; D014867:Water