Unequal effect of ethanol-water on the stability of ct-DNA, poly[(dA-dT)]2 and poly(rA)·poly(rU). Thermophysical propertiesElectronic supplementary information (ESI) available: Fig. 1S to 7S and Tables S1 to S21. See DOI: 10.1039/c4cp03459g

• Main Authors: Ruiz, Rebeca, Hoyuelos, Francisco J, Navarro, Ana M, Leal, José M, García, Begoña
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c4cp03459g

Ethanol affects unequally the thermal stability of DNA and RNA. It stabilizes RNA, while destabilizing DNA. The variation of the relative viscosity ( η / η 0 ) of [poly(dA-dT)] 2 with temperature unveils transitions close to the respective denaturation temperature, calculated spectrophotometrically and calorimetrically. From the raw data densities and speeds of sound, the volumetric observables were calculated. In all cases studied, a change in sign from low to high ethanol content occurred for both partial molar volume ( V ) and partial molar adiabatic compressibility ( K S ). The minima, close to 10%, should correspond to the highest solvation and the maxima, close to 30%, to the lowest solvation. For 40-50% ethanol, the solvation increases again. The complex structure of ethanol-water, for which changes are observed in regions close to such critical concentrations, justifies the observed behaviour. The variation of V and K S was sharper for RNA compared with respect to DNA, indicating that the solvation sequence is poly(rA)·poly(rU) < ct-DNA < [poly(dA-dT)] 2 . Molar apparent volumes ( V ) show that solvation depends on the ethanol content and type of polynucleotide, in the sequence poly(rA)·poly(rU) < ct-DNA < [poly(dA-dT)] 2 .