1∕f fluctuations of DNA temperature at thermal denaturation

We theoretically investigated the temperature fluctuations of DNA close to denaturation and observed a strong enhancement of these fluctuations at the critical temperature. Although in a much lower frequency range, such a sharp increase was also reported in the recent experimental work of Nagapriya et al. Phys. Rev. Lett. 96 038102 (2006)]. We showed that there is instead no enhancement of temperature fluctuations when the dissipation coefficient γ in Langevin equations is assumed to be larger than a few tens of ps⁻¹, and pointed out the possible role of the solvent in real experiments. We sought for a possible correlation between the growth of large bubbles and the enhancement of temperature fluctuations but found no direct evidence thereof. Finally, we showed that neither the enhancement of fluctuations nor the 1∕f dependence are observed at the scale of a single base pair, while these properties show up when summing the contributions of a large number of base pairs. We therefore conclude that both effects result from collective motions that are facilitated by the divergence of the correlation length at denaturation.