First passage times of driven DNA hairpin unzipping.

We model the dynamics of voltage-driven transport of DNA hairpins through transmembrane channels. A two-dimensional stochastic model of the DNA translocation process is fit to the measurements of Mathé, who pulled self-hybridized DNA hairpins through lipid-embedded alpha-hemolysin channels. As the channel was too narrow to accommodate hybridized DNA, dehybridization of the hairpin became the rate-limiting step of the transport process. We show that the mean first passage time versus voltage curve for the escape of the DNA from the transmembrane channel can be divided into two regions: (1) a low-voltage region where the DNA slides out of the pore in reverse and without undergoing significant dehybridization, and (2) a region where the DNA dehybridizes under the influence of the applied voltage and translocates across the membrane.