FIGURE 3. Electrolytic Characterization of Nanopore and Translocation of DNA.

The upper inset to Fig.(a) is a TEM image of a nanopore (slightly out of focus to exaggerate the pore) in a nominally 10 nm thick nitride membrane viewed at 0° tilt angle. The apparent radius of the pore is R_p =0.5±0.1nm. The lower inset is a schematic representation of the structure inferred from tilted TEM images of similar pores. The current-voltage characteristic of the nanopore is approximately linear. Figure (a) is a measurement of the I-V characteristic obtained in 1M KCl, corresponding to the nanopore shown in the inset. The fit through the data (red dashed line) has a slope of 0.63±0.03nS. When DNA is inserted at the negative electrode, transients are observed in the ionic current through the nanopore associated with a blockade by DNA. Figure (b) shows the current through the same nanopore as a continuous function of time with 50mer poly(dT) ssDNA inserted at the negative electrode (blue) and without it (red). Corresponding to the observation of transients, DNA is found at the positive electrode. Figure (c) illustrates the variety of transients observed in the same pore for an applied voltage of 200mV(i,ii,iii) all plot on the same linear scale, but each transient has been offset for clarity. The blocking current is observed to vary during the transient and from transient to transient as well. The width of the transients ranges from the bandwidth-limited 100μsec to 10msec. Taken from reference ³³.