Molecular Interactions between L-Phenylalanine and Uracyl in an Aqueous Buffer Solution at 293–323 K

Abstract

Interactions between L-phenylalanine (Phe) and uracyl (Ura) in an aqueous buffer solution (pH 7.35) are analyzed via densimetry and differential scanning calorimetry. Experimental values of the density and specific heat capacity of Ura–buffer, Phe–buffer, and Phe–Ura–buffer systems are obtained at T = (293.15, 303.15, 313.15, and 323.15) K, Ura concentrations of 0.0040 to 0.0365 mol kg−1, and a constant Phe concentration of 0.0120 mol kg−1. It is shown that the interaction between Phe and Ura is accompanied by the formation of a complex with the composition 1 : 2. It is established that the partial molar properties of Ura when it is transferred from the buffer to the buffer Phe solution are positive for the volume and negative for the heat capacity in the investigated range of temperatures. The final results are discussed using the Gurney model.