Coupled dynamics between DNA double helix and hydrated water by low frequency Raman spectroscopy

Low frequency Raman spectra (±50 cm−1) of DNA gels from 0 to −140 °C have been obtained. A drastic spectral change near −20 °C has been observed, and this is well explained by the model of coupled dynamics between the collective vibrational mode of the DNA and the relaxational mode of the secondary hydration shell. The obtained relaxation time of the secondary hydration shell at 0 °C is τ≈4×10−12 s which is the same order as that of bulk water.