Experiments of poly(dT)20 electrophoresis throughα-hemolysin nanopores were performed to unveil the electrophoretic transport mechanism of DNA through nanopores in high concentration potassium chloride solution. It...
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Experiments of poly(dT)20 electrophoresis throughα-hemolysin nanopores were performed to unveil the electrophoretic transport mechanism of DNA through nanopores in high concentration potassium chloride solution. It is found that there are two obvious current blockades induced by poly(dT)20 translocation and collision events. Both blockade currents increase linearly with the applied bias voltage. However, the normalized blockade currents are almost kept the same although variable bias voltages are applied. The collision time of poly(dT)20 in the luminal site of the pore remains constant for different voltages. The translocation speed of poly(dT)20through the nanopore decreases with the increase of bias voltage. It is because as the potential increases, the drag force on the homopolymer helps it to crumple into a cluster much easier due to the poor stacking of thymine residues compared with homopolymers consisting of other nucleotides. Molecular dynamics simulations further confirm the experimental results. Increasing the applied bias voltage can slowdown the translocation velocity of the flexible poly(dT)20, which favors increasing the precision of single molecule detection by using nanopores.
Aiming at the issues of controlling the translocation speed of DNA through a solid-state nanopore and enlarging the signal-to-noise ratio of ionic current modulation, which are challenges for the application of nanopo...
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Aiming at the issues of controlling the translocation speed of DNA through a solid-state nanopore and enlarging the signal-to-noise ratio of ionic current modulation, which are challenges for the application of nanopore technology in DNA detection, salt concentration gradients are applied across the nanopore to investigate their influence on the DNA translocation time and signal-to-noise ratio. Experimental data demonstrates that, in symmetric concentration conditions, both the current blockade and dwell time for A-DNA translocation through a solid-state nanopore increase along with potassium chloride concentration. When the concentration in the trans chamber is decreased from 1 to 0.1 mol/L, keeping the concentration of the cis chamber at 1 mol/L, the normalized current blockade is found to be increased by one order. The increased dwell time and enhanced signal-to-noise ratio are achieved with salt gradients across the nanopore, which can improve the sensitivity when detecting DNA samples.
The surface and adhesion forces between chitosan- coated mica surfaces in an acetic acid buffer solution were measured using a surface force apparatus (SFA). The force- distance profiles were obtained under differen...
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The surface and adhesion forces between chitosan- coated mica surfaces in an acetic acid buffer solution were measured using a surface force apparatus (SFA). The force- distance profiles were obtained under different pressure conditions. It was found that the chitosan was adsorbed on the mica surface and formed a stable nanofilm under acid conditions. The adsorbed chitosan nanofilms induced a short- range monotonically steric force when two such surfaces came close in the acid buffer. The adhesion forces between the two chitosan-coated mica surfaces varied with the loads. Strong adhesion between the two chitosan-coated mica surfaces was observed at high pressure. Such pressure-dependent adhesion properties are most likely related to the molecular configurations and hydrogen bonds reordering under high confinement.
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