Dielectric study on dynamics and structure of water bound to DNA using a frequency range 107-1010 Hz

Abstract

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.

Effects of pH on Dielectric Relaxation of Montmorillonite, Allophane, and Imogolite Suspensions

“…The relaxation strength due to bound water of gellan gum shows a drastic change at the gel-solution transition point (28). There is a difference in the relaxation strength between B-form DNA and randomly coiled DNA, and thus water bound to the former constructs a highly aligned cluster, and that to the latter is in disordered alignment (29). Figure 8 shows the relaxation strength due to bound water, normalized by the strength at the lowest pH of each clay, against the pH.…”

Dielectric-Relaxation Spectroscopy of Kaolinite, Montmorillonite, Allophane, and Imogolite under Moist Conditions

“…Our focus is on ascertaining the relaxation parameters of bound H20, especially the relaxation time. By using this method, bound H20 was confirmed in biopolymers, such as DNA (Mashimo et al, 1989), globular protein (Miura et al, 1994), aqueous solutions, and moist collagen (Shinyashiki et al, 1990). For moist collagen, the relaxation strength observed at 100 MHz depends on the water content and does not occur for dried collagen.…”

Terahertz dynamics of water before and after water shedding from reverse micelles

“…The results obtained from averaging the time constants with the standard deviation of the mean are presented below. There is a question concerning the uniqueness of the time constants derived from the curve fitting, although multi-parameter fitting is a common method for spectral analysis [32][33][34][41][42][43]; in fact, as shown for liquid water in Fig. 6(a), there is a small difference between the time constants due to the measurements in the different frequency ranges [32,40].…”