TRANSFER ENERGETICS OF SOME NUCLEOSIDES IN AQUEOUS MIXTURES OF UREA AND GLYCEROL

Standard free energies (Delta G(t)(0)) and entropies (Delta S-t(0)) of transfer of some nucleosides viz. adenosine (ado), guanosine (guo) an d xanthosine (xao) from water to aqueous mixtures of urea (UH) and gly cerol (GL) have been evolved from solubilities measured at different t emperatures. The observed Delta G(0)-composition profiles show increas ing stabilization for the nucleosides in both the cosolvent systems. T he T Delta S-t(0)-composition profiles are, however, complicated. So, after the elimination of various interaction effects, viz. cavity, dip ole-dipole, dipole-induced dipole and dispersion interactions, the res ults have been discussed in the light of the hydrophilic-hydrophobic h ydration effect. The solvation behaviour of the nucleosides in UH-wate r and GL-water mixtures help understand the relative stability of the double stranded nucleic acid helix in these two cosolvent systems.