Fig. 6. Charge selectivity regulating peptide translocation through pPorA variants. (a) Electrical recordings showing D9 interaction with single pPorA-K24 (10 μM, cis) at +10 mV and +50 mV. (b) Electrical recordings showing R9 interaction with single pPorA-A24 (0.5 μM, cis) at −5 mV and −20 mV. Electrolyte: 0.15 M KCl, 10 mM HEPES, pH 7.4. Inset, recording at expanded time scale and the corresponding τ_off dwell time histogram. Model showing pPorA charge pattern. The current signals (a) were filtered at 2 kHz and sampled at 10 kHz and (b) −5 mV and −20 mV were digitally filtered at 4 kHz and 7 kHz using an 8-pole Bessel digital filter.