| Budget Amount *help |
¥1,800,000 (Direct Cost: ¥1,800,000)
Fiscal Year 1988: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1987: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Research Abstract |
The nature of the interaction between DNA and sodium ion was investigated by sound velocity. When aquous solution of DNA was titrated with concentrated solution of NaCl, the sound velocity, i.e., the adiabatic compressibility of the solution changes linearly with added salt concentration. If there is strong interaction between counterion and polyion accompanying changes of hydration volumes, the sound velocity dose not change linearly. In the case of polyphosphate (PP) solutions, the increase of sound velocity of the solutions dose not change linearly and shows a breaking point. Na^+ ion below the braking point binds to PP so that Na^+ may perturb the hydration layer around PP. The degree of ion binding obtained from the breaking point is ca. 0.25. the degree of ion binding of PP obtained from the activity measurement was estimated as fa 0.3, which gives the degree of ion binding due to atmospheric interaction between ions. Therefore, Na^+ is strongly attracted by PP^-. In the case of DNA, fa 0. but Na^+ ion bound to the hydration layer was not detected. These results indicate that the interaction between DNA and Na^+ is atmospheric one and the hydration layer around DNA is scarcely perturbed by approach of Na^+, since phosphate ion in DNA is surrounded by bases, such as adenine, thymine and so on and the charge density of DNA is low in comparison with that of PP.
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