NUCLEAR TRACK-ETCHED FILTERS AS MODEL PORES FOR BIOLOGICAL-MEMBRANES

Ion current through individual pores in track-etched polyethyleneterephthalate filters can have the following properties which are shared by a number of biological ion channels: 1) selectivity for cations over anions, or vice versa depending on the surface charge of the filter and the diameter of the pore; 2) fluctuations between high- and low-conductance states; 3) inhibition by protons and divalent cations with efficacy H+ > Zn2+ > Ca2+ approximate to Mg2+. Pore topography in differing states can be imaged by scanning probe microscopy. We conclude that track-etched filters provide a useful model system for studying the physical and chemical basis for some of the characteristic behaviour of biological channels.