The effect of Cs+ and Na+ on the buoyant density and hydration of native DNA in 20 mM salt

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Organism Unspecified
Reference Birnie GD, MacPhail E, Rickwood D. Isopycnic sedimentation of DNA in metrizamide: the effect of low concentrations of ions on buoyant density and hydration. Nucleic Acids Res. 1974 Jul1(7):919-25. p.922 table 2PubMed ID10793724
Primary Source Cohen G, Eisenberg H. Deoxyribonucleate solutions: sedimentation in a density gradient, partial specific volumes, density and refractive index increments, and preferential interactions. Biopolymers. 1968 6(8):1077-100.PubMed ID5663407
Comments P.923 2nd & 3rd paragraph:"The effect of a change in counter-ion on the buoyant density of DNA was examined by comparing the buoyant densities of CsDNA and NaDNA. The results are summarized in Table 2. Since there is a marked difference between the partial specific volumes of CsDNA and NaDNA [primary source], it was to be expected that the buoyant densities of these salts of DNA would also differ markedly in metrizamide gradients. However, the buoyant densities of CsDNA and NaDNA differ to a greater extent than can be accounted for simply by the difference between their partial specific volumes. When this difference is taken into account it appears that CsDNA is considerably less hydrated than NaDNA and, moreover, that the hydration is decreased by the same amount in both chloride and sulphate solution. Table 2 also shows that the buoyant densities of both CsDNA and NaDNA are lower in the presence of chloride ions than in the presence of sulphate ions. This suggested that anions, as well as cations, may have a significant effect on the net hydration of DNA." Primary source investigated calf thymus DNA
Entered by Uri M
ID 112348