In a recent experiment, a single DNA double helix is stretched and relaxed in the presence of spermidine, a short positive polyelectrolyte, and the pulling force is measured as a function of DNA extension. In a certain range of spermidine concentration, a force plateau appears whose value shows maximum as a function of spermidine concentration. We present a quantitative theory of this plateau force based on the theory of reentrant condensation and derive almost parabolic behavior of the plateau force as a function of the logarithm of the spermidine concentration in the range of condensation. Our result is in good agreement with experimental data.
|Original language||English (US)|
|Number of pages||8|
|Journal||Physica A: Statistical Mechanics and its Applications|
|State||Published - Apr 15 2005|
Bibliographical noteFunding Information:
The authors are grateful to A.Yu. Grosberg, Y. Murayama, Y. Rabin, I. Rouzina, and J. Zhang for useful discussions. This work is supported by NSF No. DMR-9985785 and DMI-0210844.
- Pulling force