The dielectric behavior of living tissues and a number of biological materials was examined by new equipment of the time domain reflectometry method in a wide frequency range of 107-1010 Hz. We found two peaks of Debye absorption around 100 MHz and 20 GHz fpr all the materials. The low-frequency absorption is probably due to bound water while the high-frequency absorption to free water. From the observed relaxation times of bound water a hypothesis is ventured on the structure of bound water and its relaxation mechanism.

Dielectric measurements over a microwave frequency range 10 MHz–15 GHz were carried out by the use of new time domain reflectometry equipment on the mixtures of water with five primary alcohols, viz., methanol, ethanol, and n-propanol in the concentration range 0≤x≤1 and n-butanol and amyl alcohol in the range 0≤x≤0.5 at room temperature; x being the mole fraction of water. The systems of water and two alcohols of low molecular weight are characterized by a single relaxation with a distribution parameter of the unity or near to it. The molecular reorientation in the mixtures as well as water and these alcohols is a cooperative process involving a large number of molecules with the hydrogen-bond linkages (O–H⋅⋅⋅O). Dielectric behavior of the mixtures of water and methyl or ethyl alcohol is due to the structure of a hydrogen-bonded network being microscopically homogeneous. Microscopic heterogeneity occurs in the mixtures of water and higher alcohols.

Dielectric relaxation peak due to bound water was found around 100 MHz in poly(dG-dC).poly(dG-dC) and calf thymus DNA in water-ethanol mixtures with NaCl buffer. Relaxation time and strength show a transition for poly(dG-dC).poly(dG-dC) at an ethanol composition Cw = 0.45 (w/w) where the structural transition from B- to Z-DNA takes place. It has been suggested that the transition is caused by removal of the bound water molecules preferentially from the phosphate groups. If the bound water molecules are removed equally from the phosphate groups and the grooves, the structural transition from B to A takes place. By analogy with hydration of tropocollagen, it was found that 19 water molecules per one nucleotide are at least necessary to keep B-DNA. Thirteen molecules are bound to A-DNA and 9 molecules to Z-DNA. Stringlike multimers are proposed as available structures of the bound water.

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vibrational frequency is perturbed by the weak dipole-dipole interaction between SCN" ion and solvent. This interaction with solvent is not strong enough to generate a new Raman band but the interaction affects the vibrational frequency of the CN stretching mode. It is noted that the formation of the contact ion pair, such as LiNCS and NH4NCS, gives rise to a new Raman band, as mentioned above.Two Raman bands of the CS stretching mode are observed, corresponding to the hydrated free SCN" ion and free SCN" ion surrounded by DMF molecules. On the other hand, only one Raman band is observed for the CN stretching mode. At this stage, it is difficult to interpret the different behavior of the Raman bands but one interpretation is that the band splitting of the CN stretching mode may be smaller than for the CS band, since the CN bond has a triple bond character and is more tight than the CS bond.The dynamic nature of SCN" ion is affected by the interaction between SCN" ion and solvent. The covib for water is very broad in comparison with that for DMF. Rothschild et al. interpreted the broad Raman line shape of the CN stretching mode in water in terms of the motion characteristic of water molecules and a water cage around SCN" ion.24 As is seen in Figure 4, the tovib abruptly decreases beyond 60 mol % of DMF; that is, the vi-brational relaxation of SCN" ion is affected by the change of the composition in mixtures. The SCN" ion may be surrounded by water molecules up to 60 mol % DMF and above that composition the environment of free SCN" ion is perturbed by DMF molecules and counterions. The rough estimation of the reorientational correlation time is 2.2 ps for free SCN" and 3.8 ps for ion-paired LiNCS. The reorientational times weakly depend on the composition of the mixtures. The larger value of 0 for DMF compared with water indicates that the reorientational motion of free SCN" ion is less hindered in DMF than in water. It is reasonable that ion-pair formation should result in slowing the reorientational motion, as shown in Figure 4.In conclusion, the dissolved state of SCN" ion in water-DMF mixtures abruptly changes around 60 mol % of DMF. Below this composition SCN" ion interacts weakly with the surrounding water molecules and above this composition ion pair and/or free SCN" ion surrounded by DMF molecules are dominant in the mixtures.