Fig. 1: Complexity and diversity of ion transport in single aerolysin pores.

a, Not-to-scale schematic of the experimental set-up. A lipidic membrane separating two reservoirs filled with electrolyte (cations are shown in blue; anions are shown in red) with a single aerolysin wt pore incorporated; the current through the pore is measured via Ag/AgCl electrodes. b, Typical single-pore IV curve where the current of the open pore is measured at different voltages consecutively. A slight rectification is visible and indicated through arrows at ±100 pA. Inset: the voltage trace that can be used to acquire such data. c, Absolute current over time traces at constant potential of a single aerolysin wt nanopore. The same pore is measured first at 100 mV (green) and then at −100 mV (red) for 240 s. Rectification is clearly visible as the absolute current is higher at −100 mV. At 100 mV, the measured current is constant, while at −100 mV, the current decreases spontaneously; this behaviour is referred to as gating. d, Left: 39 gating traces recorded for 1 single aerolysin wt pore at −160 mV, coloured by current, showing the diversity of gating states associated with different current levels. The overlay is a zoom-in of the area shaded in grey. After recording the pore in the gated state, a bias of 0 mV was applied to open the pore. Right: violin plot of gating (red) and open-pore (green) current levels measured in 4 different single pores (replicate experiments) at −160 mV. Each randomly offset point in the violin plot represents the average of the gating or open-pore current of one gating trace. The white error bar denotes ±1 standard deviation of the mean of the average closed-state currents. The large variation in closed-state current compared to open-pore current variation suggests a stochastic phenomenon. All experiments are done in 1 M KCl buffered to pH 6.2 with 10 mM phosphate.