Figure 4.

Capture and immobilization of A₆₀-Btn-Strep in γ-HL. (a) Schematic showing: (I) open channel of γ-HL; (II) electrophoretically captured ssDNA exploring the vestibule; (III) ssDNA threading through the β-barrel; (IV) release of ssDNA by reversing the potential polarity. The ssDNA [poly(dA)₆₀] (green) is attached to streptavidin (blue) using a biotin linker (orange). (b) Left: sample I-t trace labeled with proposed steps, (I)-(IV). Right: expanded view of the mid-level blocking current indicated in the red box. Recordings were carried out at −120 mV, in 3 M KCl, 20 mM HOAc/KOAc, pH 5.0, at 20 °C. The I-t traces were post-filtered at 2 kHz for presentation. Open-channel current (I₀), mid-level blockade ($I_{\mathrm{M}}^{\mathrm{B}\mathrm{t}\mathrm{n}}$), and deep current blockade $I_{\mathrm{r}\mathrm{e}\mathrm{s}}^{\mathrm{B}\mathrm{t}\mathrm{n}}$ correspond to (I), (II), and (III), respectively.