Fig. 1.

(a) Representative current trace showing the Level-1 and Level-2 events for trapping C30 in the pore from the cis side in both orientations, and short spikes for translocation of the unhybridized strands of C30. This current was recorded at +100 mV in 1 M KCl, 10 mM Tris (pH 7.5) and in the presence of 100 nM of each strand of C30 in the cis solution. The DNA sequences are shown in Table 1; (b) fractions of Level-1 and Level-2 events for C30 at various voltages. The majority of C30 block events were Level-1 events, indicating the preference for trapping the overhang over the blunt end in the pore; (c) duration of Level-1 events as a function of voltage applied. The duration–voltage correlation approximates to an exponential decay, indicating that the unzipping of C30 needs to overcome an energy barrier. The duration histograms for all voltages are illustrated in Fig. S2.^†