Predicted role of particular phonons in the strand separation melting of the DNA double helix.

The frequency-dependent vibrational fluctuation of the hydrogen bonds around a nucleation defect for the strand separation melting of a DNA polymer poly(dG)-poly(dC) is studied using a modified self-consistent phonon theory. There are two critical frequency bands around the defect at 340 K which is near the temperature at which the hydrogen bonds in neighboring cells melt. The first band is between 60 cm-1 and 120 cm-1 which is essential for the melting proceeding in +z direction(3'----5' in the G backbone). The second is the band under 20 cm-1 which is important for the melting proceeding in -z direction.