Solvation behavior of some nucleic acid bases and nucleosides in water and in aqueous guanidine hydrochloride solutions: Viscometric, calorimetric and spectroscopic approach

• B values are positive for nucleic acid bases and nucleosides in aqueous GnHCl.
• Standard molar enthalpy of transfer is exothermic.
• Transfer parameters support the strengthening of hydrophilic–ionic interactions.
• Loss of π–π∗ maxima of solutes at higher molalities of GnHCl.
• Increased concentration of GnHCl leads to formation of plateau at 230 nm.

Viscosity, η and enthalpy of dilution, q of studied 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 (GnHCl) have been determined over a temperature range (288.15-318.15) K at (101.3 ± 0.5) kPa. These data have been used to calculate viscosity B-coefficients and standard molar enthalpy of dilution, ΔdilHo which have further been used to evaluate corresponding transfer parameters ΔtrB and ΔtrΔdilHo, respectively. Positive ΔtrB values and negative ΔtrΔdilHo values indicate the predominance of hydrophilic–ionic interactions in these systems. Temperature dependence of B-coefficient and ΔdilHo has also been discussed. Spectroscopic studies have been carried out to further investigate the structural changes and the interactions involved in the mixed aqueous solutions.

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