Force-induced melting of the DNA double helix 1. Thermodynamic analysis.
The highly cooperative elongation of a single B-DNA molecule to almost twice its contour length upon application of a stretching force is interpreted as force-induced DNA melting. This interpretation is based on the similarity between experimental and calculated stretching profiles, when the force-dependent free energy of melting is obtained directly from the experimental force versus extension curves of double- and single-stranded DNA. The high cooperativity of the overstretching transition is consistent with a melting interpretation. The ability of nicked DNA to withstand forces greater than that at the transition midpoint is explained as a result of the one-dimensional nature of the melting transition, which leads to alternating zones of melted and unmelted DNA even substantially above the melting midpoint. We discuss the relationship between force-induced melting and the B-to-S transition suggested by other authors. The recently measured effect on T7 DNA polymerase activity of the force applied to a ssDNA template is interpreted in terms of preferential stabilization of dsDNA by weak forces approximately equal to 7 pN.
Rouzina
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Department of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, 1479 Gortner Avenue, St. Paul, Minnesota 55108, USA. rouzina@biosci.umn.edu
Bloomfield
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D055592:Biophysical Phenomena; D001703:Biophysics; D004247:DNA / Q000737:chemistry*; D019277:Entropy; D066298:In Vitro Techniques; D007700:Kinetics; D008956:Models, Chemical; D008958:Models, Molecular; D009691:Nucleic Acid Denaturation; D013816:Thermodynamics
D004247:DNA