title: DNA unzipped under a constant force exhibits multiple metastable intermediates.
abstract: Single molecule studies, at constant force, of the separation of double-stranded DNA into two separated single strands may provide information relevant to the dynamics of DNA replication. At constant applied force, theory predicts that the unzipped length as a function of time is characterized by jumps during which the strands separate rapidly, followed by long pauses where the number of separated base pairs remains constant. Here, we report previously uncharacterized observations of this striking behavior carried out on a number of identical single molecules simultaneously. When several single lambda phage molecules are subject to the same applied force, the pause positions are reproducible in each. This reproducibility shows that the positions and durations of the pauses in unzipping provide a sequence-dependent molecular fingerprint. For small forces, the DNA remains in a partially unzipped state for at least several hours. For larger forces, the separation is still characterized by jumps and pauses, but the double-stranded DNA will completely unzip in less than 30 min.
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Claudia
authors.initials: C
authors.lastname: Danilowicz
authors.forename: Vincent W
authors.initials: VW
authors.lastname: Coljee
authors.forename: Cedric
authors.initials: C
authors.lastname: Bouzigues
authors.forename: David K
authors.initials: DK
authors.lastname: Lubensky
authors.forename: David R
authors.initials: DR
authors.lastname: Nelson
authors.forename: Mara
authors.initials: M
authors.lastname: Prentiss
mesh_terms: D000327:Adsorption; D004247:DNA / Q000737:chemistry*; D008962:Models, Theoretical; D009690:Nucleic Acid Conformation
chemical_list: D004247:DNA