Frictionless sliding of single-stranded DNA in a carbon nanotube pore observed by single molecule force spectroscopy.

Smooth inner pores of carbon nanotubes (CNT) provide a fascinating model for studying biological transport. We used an atomic force microscope to pull a single-stranded DNA oligomer from a carbon nanotube pore. DNA extraction from CNT pores occurs at a nearly constant force, which is drastically different from the elastic profile commonly observed during polymer stretching with atomic force microscopy. We show that a combination of the frictionless nanotube pore walls and an unfavorable DNA solvation energy produces this constant force profiles.