Partial Molar Isentropic and Isothermal Compressions of the Nucleosides Adenosine, Cytidine, and Uridine in Aqueous Solution at 298.15 K

Abstract

Sound speeds have been measured for aqueous solutions of the nucleosides adenosine, cytidine, and uridine at T = 298.15 K and at ambient pressure. For adenosine and uridine, the partial molar isentropic compressions at infinite dilution, KS,2o, were derived from the sound speed data using conventional methods. These KS,2o results were combined with the partial molar heat capacities and partial molar isobaric expansions at infinite dilution available from the literature to evaluate, for the first time, the partial molar isothermal compressions at infinite dilution, KT,2o {KT,2o = −(∂V2o/∂p)T, where V2o is the partial molar volume of the solute at infinite dilution}. An alternative method is described for the calculation of the KS,2o and KT,2o values for cytidine from the sound speed data. The KT,2o results for the nucleosides have been rationalized in terms of the likely solute−water interactions. For cytidine, an analysis of the molality dependence of the partial molar isothermal compression in terms of self-association has also been explored.