To understand the mechanism by which individual DNA molecules partition into a nanometer-scale pore, we studied the concentration and voltage dependence of polynucleotide-induced current blockades of single a-hemolysin ionic channels. At fixed single-stranded DNA concentration and magnitude of the applied transmembrane potential, DNA enters more readily from one side of the pore than the other. We show that the blockade frequency increases exponentially as a function of the applied potential and is proportional to the polymer concentration. We directly measure the value of the electrical potential that confines a modified version of the polymer inside the nanopore against random diffusion and repulsive forces. We also show that a minimum length polynucleotide is required for the polymer and the pore to interact for times that exceed the diffusion limit. Several candidate models for the interactions between polynucleotides and the pore are discussed.
Citation: Physical Review Letters
Pub Type: Journals
DNA, ion channel, polymer, polynucleotide, transport