Kinetics and mechanism of plasmid DNA penetration through nanopores

DNA transport through membranes is a key step in many biological processes. The phenomenon of DNA penetration through narrow polymer membrane pores was previously observed only under the influence of external electric fields. Recently, it was shown that some types of DNA could penetrate through membrane pores also under hydrodynamic pressure. Here we show that double-stranded plasmid DNA with a 350 nm hydrodynamic diameter penetrates through membrane pores as narrow as 10 nm under pressure, and suggest that the supercoiled plasmids penetrate through these narrow pores by stretching into long hair-shaped flexible strands. We study the kinetics of plasmid penetration and the changes in plasmid elasticity caused by UV irradiation. The results suggest a mechanism based on "snake-like" movement with gradual pore blocking. (C) 2011 Elsevier B.V. All rights reserved.