For the same voltages, the electric field intensity in our pore is less than that of a small nanopore (10 nm). As the applied voltage increases to 300 mV, the electric field distribution is comparable to that of a smaller nanopore (10 nm) at the applied voltage of 120 mV. The electric field strength (E) along the center axis of the pore is also shown in Figure 2c. It is clear that the distribution OICR-9429 order of the electric field is approximately uniform in the pore while it is sharply decayed in the pore mouth. Thus, protein translocation through nanopores crosses over from almost purely diffusive to drift-dominated motion. There is a characteristic length scale

that exists in the pore mouth for two forms of protein motion, which can be described by the Smoluchowski theory with a capture radius of r*[35, 44]: (1) Here d p and l p are the diameter and length of the pore, respectively, μ is the electrophoretic mobility, D is the protein diffusion coefficient, and φ is the biased voltage. This shows that the capture radius grows with the pore diameter and the biased voltages, and a bigger capture area can make more proteins trapped into the nanopore. Thus, a high throughput is expected in our nanopore https://www.selleckchem.com/products/AZD2281(Olaparib).html device, which is also confirmed in our studies behind. In addition, it is worth to mention the current noise in solid-state nanopores,

which involves the 1/f-type excess noise and other contributions [45, 46]. The 1/f-type noise is related to the fluctuation of charge carriers. As the voltage increases, the accelerated motion of charge carries will cause local ion aggregation in the nanopore, resulting in the CHIR-99021 order increase of 1/f-type excess

noise. It can be confirmed from the noise power spectra Methane monooxygenase observed in our experiment (not shown here) and other experiments [45, 46]. Protein transport at the medium-voltage region When the applied voltage is higher than 300 mV, a set of transient downward spikes appears, indicating the translocation of a single protein molecule across the pore. After confirming the ability of our large nanopore with a detectable signal-to-noise ratio, the voltage effects on the translocation signal have been studied in detail. Current blockage signals from individual molecular translocations can be characterized by the time duration (t d) and the magnitude of the blockage current (ΔI b). The histograms of the magnitude and dwell time of the transition events are characterized in our work. As shown in Figure 3, the amplitude distribution of blockage events at each voltage is fitted by a Gaussian mixture model. Based on the fitting curves, the peak values of the current blockages at 300, 400, 500, and 600 mV are 298, 481, 670, and 848 pA, respectively, which correspond to the most probable current drops induced by a single protein through the nanopore at varied voltages. The current amplitude linearly increases with the voltages, which yields a slope of 1.