Spin-echo technique study of the non-rotational hydration of deoxyribonucleic acid

The non-rotational hydration of DNA and its correlation time have been investigated by the NMR spin-echo technique. Relaxation times T₁ and T₂ were measured at 20° and the dependence of the values of T₁ and T₂ on the DNA concentration was established. The theory of this phenomenon is discussed. The non-rotational amount of water was shown to be dependent on the molecular weight of the DNA, ranging from about 8 to 10% with molecular weights of 6·10⁶ to 7·7·10⁶. The non-rotational hydration represents only a part of the total water present in hydration shells. Denaturation of the DNA decreases the non-rotational hydration 1.45 times as compared with native DNA simultaneously resulting in an increase in the correlation time, τ_c, by a factor of 1.45. Denatured DNA molecules have distinctly less freedom of movement than double-helix DNA which has a high degree of structural organization.