By the use of the time domain reflectometry method dielectric measurements were carried out first on methanol mixtures with ethanol and 1-propanol, and second, water mixtures with methanol, ethanol and 1-propanol in the frequency range 10 MHz–20 GHz. The first mixtures show a Debye relaxation and logarithm of the relaxation time is given by a linear function of the mole fraction of methanol. These mixtures have the same chainlike cluster of pure alcohol. The second mixtures show the same trend of the relaxation time in a region 0≤xw<0.83, where xw is the mole fraction of water. In a region 0.83<xw≤1.0, we observe an entirely different behavior, which indicates that the cluster of pure water appears for xw>0.83 and that the cluster must be cyclic, consisting of six molecules.

Dielectric relaxation measurements over an extremely wide frequency region from 1 MHz to 20 GHz were performed on water mixtures with glucose, polysaccharides, and L-xylo ascorbic acid by the use of time domain refiectometry. For mixtures of polysaccharides bigger than maltotriose, two relaxation peaks were definitely observed. The high frequency relaxation is the water relaxation and the low frequency one is due to orientation of polysaccharide molecules. In the case of glucose, only one relaxation peak could be observed. It is shown that a hexagonal cluster in the lattice of ice can be replaced easily by the glucose molecule, where the lattice is distorted slightly, but stabilized by several hydrogen bonds between the glucose molecule and the lattice. Although the cluster can be replaced by the L-ascorbic acid molecule too, the lattice cannot be kept stable. Its water mixture shows two relaxation peaks clearly. It is suggested that water has a structure of the distorted lattice of ice. Fluctuation of the lattice breaks the hydrogen bonds and the lattice is decomposed. Orientation of the water molecules released gives rise to the relaxation concerned.

Dielectric measurements were performed on water–p-dioxane and methanol–p-dioxane mixtures using time domain reflectometry over the frequency range 0.1–10 GHz. In the case of water–p-dioxane mixtures, the relaxation strength normalized by the number of water molecules per unit volume is independent of the molar fraction of water xW if xW<0.83. There are no ordered micellelike clusters in the mixture. On the other hand, if xW is larger than 0.83, the normalized strength increases linearly with xW. The clusters of pure water which appear in this region are cyclic and consist of six molecules. In the case of methanol–p-dioxane, the normalized strength is independent of xM for xM<0.66 and increases linearly with xM for xM>0.66. However, the relaxation time of pure methanol is too large for clusters consisting of three molecules. It is suggested that the chainlike clusters form network structures.

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.

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The dynamical properties of DNA (from Escherichia coli and salmon testes) in SSC buffer were investigated by the use of the time domain reflectometry method; accurate measurements on the complex permittivity were carried out. A relaxation process due to bound water was discovered around 100 MHz in addition to the relaxation process due to free water observed around 20 GHz. The former shows a dielectric transition of the order-disorder type at the denaturation temperature Tm. Invariant temperature dependence of the relaxation strength below Tm indicates that the cluster of bound water molecules takes an ordered structure on the surface of B-form DNA. On the other hand, the negative and large temperature coefficient of the relaxation strength indicates that the cluster is thermally unstable above Tm.