Rapid switching of ion current in narrow pores: implications for biological ion channels

Ions flowing through purely synthetic filters made of polyethylene terephthalate which have been etched to produce narrow pores show: (i) rapid transitions between a high-conducting and a low-conducting state; (ii) selectivity of ion flow; and (iii) inhibition by divalent cations and protons. These features resemble those displayed by many biological ion channels. We interpret our results in terms of the special properties of ion conductance at an interface that may be observed whenever the contribution of bulk conductance is minimal.