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. 2013 Sep 3;105(5):1199–1207. doi: 10.1016/j.bpj.2013.07.047

Figure 1.

Figure 1

Measurement principle. (I) A potential of 120 mV is applied to capture a DNA molecule with an aptamer structure (red) and a thread sequence (blue) on its 3' end. While the aptamer structure is unfolded on capture, a stable hairpin (green) at the 5' end prevents the DNA from traversing the pore. (II) The DNA is held inside the pore at low bias voltage (50 mV) to allow reforming of the aptamer and target binding on the trans side. (III) A voltage ramp to −200 mV is applied. When the aptamer structure unfolds, the DNA molecule escapes from the pore and a sudden increase in the current signal is observed. The corresponding unfolding voltage is recorded.