Figure 3. Representative single-channel electrical recordings of the FhuA ΔC/Δ4L.

This single-channel trace is recorded at an applied potential of +180 mV and in 1 M KCl, 10 mM potassium phosphate, pH 7.4. Sn represents the state number of the nanopore at an applied transmembrane potential of +180 mV. S1 is the state of the nanopore before closure. S2 and S3 are the states of a partially closed nanopore. FCT is the first closure time when the nanopore undergoes its first discrete current transition from S1 to S2. The step size denotes the magnitude of the single-channel current decrease by a single closure.