Slow relaxation process in DNA

A dynamic transition at temperatures ∼200-230K is observed in many hydrated biopolymers. It shows up as a sharp increase of the mean-squared atomic displacements above this temperature range. We present neutron scattering data of DNA at different levels of hydration. The analysis shows that the dynamic transition in DNA is related to a slow relaxation process in the MHz-GHz frequency range. This slow relaxation process is completely suppressed in the dry DNA sample where no dynamic transition was observed, The nature of the slow process is discussed, We ascribe it to a global relaxation of DNA molecule that involves cooperative motion of many base-pairs and backbone.