Figure 2: Translocation of dsDNA through large diameter T pore channels.

(a) Sample trace of a current measurement through a single DNA channel incorporated into a lipid bilayer membrane in the absence of analyte molecules, performed at a transmembrane voltage of 125 mV. The green line indicates the median of the current over 100 ms (≈365 pA). (b) Current trace recorded in the presence of 527 base pair long dsDNA. The green line indicates the median of the current over 100 ms (≈385 pA). Three examples for translocation events are shown in detail below the trace. (c) Distribution of event durations extracted from current traces recorded at 75, 100 and 125 mV. The times occurring with the highest probabilities (170, 154 and 149 μs at 75, 100 and 125 mV, respectively) are defined as DNA translocation times at the corresponding voltages. The histograms were fit with a one-dimensional drift-diffusion model for nanopore translocation⁷ with the two fit parameters v and D (velocity and diffusion coefficient; cf. Supplementary Note 3). In the inset, a scatter plot of the current reduction ΔI versus the translocation time τ is shown for all events detected at 75, 100 and 125 mV. As expected, ΔI increases with voltage, while the event duration decreases. (d) Translocation velocities and event frequencies extracted from the measurements. Consistent with dsDNA translocation, both parameters increase with increasing voltage. Inset: all electrical recordings were performed with the droplet interface bilayer technique (cf. Methods). Lipid bilayers were formed at the interface between two electrically contacted droplets containing water, 1 M KCl and 5 mM MgCl₂ encapsulated by lipid monolayers made from DPhPC.