An intermembrane ion trap

Abstract

Molecular ion channels consisting of covalently stacked crown ether (CE) rings are mounted in a membrane bilayer between two ion-containing aqueous layers. Molecular dynamics shows that due to a large negative electrostatic potential on the axis of the channel, the cations (but not anions) in the electrolyte layers enter the channel. Calculations suggest that the cations encounter an energy barrier at the mouth of the channel and occupy axial sites between which they may undergo a dynamic redistribution. The application of electric fields sweep the ions to one end of the channel but fields of electrolytic strengths effect neither the exit of the cations nor the admission of anions. The retention of the ions M+ show that the CE channel acts as a trap for cations from the electrolyte layers.