Force-induced melting of the DNA double helix. 2. Effect of solution conditions

Ioulia Rouzina, Victor A. Bloomfield

Research output: Contribution to journalArticlepeer-review

166 Scopus citations


In this paper, we consider the implications of the general theory developed in the accompanying paper, to interpret experiments on DNA overstretching that involve variables such as solution temperature, pH, and ionic strength. We find the DNA helix-coil phase boundary in the force-temperature space. At temperatures significantly below the regular (zero force) DNA melting temperature, the overstretching force, fov(T), is predicted to decrease nearly linearly with temperature. We calculate the slope of this dependence as a function of entropy and heat-capacity changes upon DNA melting. Fitting of the experimental fov(T) dependence allows determination of both of these quantities in very good agreement with their calorimetric values. At temperatures slightly above the regular DNA melting temperature, we predict stabilization of dsDNA by moderate forces, and destabilization by higher forces. Thus the DNA stretching curves, f(b), should exhibit two rather than one overstretching transitions: from single stranded (ss) to double stranded (ds) and then back at the higher force. We also predict that any change in DNA solution conditions that affects its melting temperature should have a similar effect on DNA overstretching force. This result is used to calculate the dependence of DNA overstretching force on solution pH, fov(pH), from the known dependence of DNA melting temperature on pH. The calculated fov(pH) is in excellent agreement with its experimental determination (M. C. Williams, J. R. Wenner, I. Rouzina, and V. A. Bloomfield, Biophys. J., accepted for publication). Finally, we quantitatively explain the measured dependence of DNA overstretching force on solution ionic strength for crosslinked and noncrosslinked DNA. The much stronger salt dependence of fov in noncrosslinked DNA results from its lower linear charge density in the melted state, compared to crosslinked or double-stranded overstretched S-DNA.

Original languageEnglish (US)
Pages (from-to)894-900
Number of pages7
JournalBiophysical journal
Issue number2
StatePublished - 2001

Bibliographical note

Funding Information:
Supported in part by National Institutes of Health Grant GM28093.


Dive into the research topics of 'Force-induced melting of the DNA double helix. 2. Effect of solution conditions'. Together they form a unique fingerprint.

Cite this