Volumetric studies on nucleic acid bases and nucleosides in aqueous guanidine hydrochloride solutions at T = (288.15 to 318.15) K and at atmospheric pressure

Highlights: • V_2,ϕ values are positive for nucleic acid bases and nucleosides in aqueous GnHCl. • Δ_trV_2,ϕ^o indicate salting-out at lower and salting-in effect at higher concentrations. • Competing hydrophilic and hydrophobic interactions are concentration specific. • Model compounds mimic the pattern of interactions occurring in nucleic acids. - Abstract: Apparent molar volumes (V_2,ϕ) have been determined from density measurements for some nucleic acid bases (uracil, cytosine, thymine), and nucleosides (uridine, cytidine and thymidine) in water and in aqueous solutions of (0.10, 0.25, 0.50, 0.75 and 1.00) mol ⋅ kg⁻¹ guanidine hydrochloride (co-solute) over the temperature range (288.15 to 318.15) K, at atmospheric pressure using vibrating-tube digital densimeter. These data have further been used to calculate apparent molar volumes V_2,ϕ^o at infinite dilution and the corresponding apparent molar volumes of transfer Δ_trV_2,ϕ^o at infinite dilution from water to aqueous solutions of guanidine hydrochloride (GnHCl). Apparent molar expansibilities (E_2,ϕ^o), second-order derivative (∂²V_2,ϕ^o/∂T²)_p and volumetric interaction coefficients have also been calculated. Co-sphere overlap model has been used to rationalize the data in terms of molecular interactions (hydrophilic, hydrophobic and ionic interactions). The present data have been compared and discussed for the systems studied with those reported in the presence of other co-solutes. The contributions of –CH₂ group to V_2,ϕ^o have also been calculated at different temperatures and concentrations of GnHCl