The thermally stimulated depolarization current (TSDC) measurements in
frozen aqueous solutions, gels and solid layers of NaDNA show typical
ly up to three dipolar overlapping peaks in the low-temperature range
of 80 - 150 K. Up to four discrete relaxation peaks have been observed
at higher temperatures above 150 K. The low-temperature TSDC peaks ar
e due to the dipolar relaxations of free and loosely bound water which
crystallizes. Part of bound water especially in the first hydration s
hell of DNA molecule is at low temperatures in the form of glass. The
transition of this glass from solidlike behavior to liquidlike behavio
r observed mainly in gels and solid samples is associated with a previ
ously founded TSDC relaxation peak. The peak is at its maximum at 165
- 250 K depending on the sample humidity. Existence of this relaxation
in the samples with water contents in a broad range confirms, that th
e slowly relaxing shell (minimally 5 - 7 water molecules / nucleotide)
closely associated with DNA double helix retains its characteristics.
Also another peak of the high-temperature band at 180 - 205 K which w
as observed in the samples at hydration 2 - 1800 g H2O/g dry NaDNA is
due to a relaxation in the sample volume. At the highest temperatures
relax the space charges trapped at the electrodes.