Thermodynamics and the mechanism of interaction of adenine with amino acids in water

Two groups of amino acids, which react differently with adenine, are distinguished. In the case of nonpolar and aliphatic amino acids, the endothermic effect of dehydration plays a decisive role, while in the case of aromatic, polar, and charged amino acids the exothermic effect of interaction with adenine is dominant. Associates of Ade with Lys. HCl, His, Trp, Asp, and Glu were found. It was demonstrated that the complex-forming ability of purines (Ade and Caf) is higher than that of pyrimidines. Based on the linear enthalpy-entropy compensation effect for complexes of amino acids with adenine, it was suggested that the hydration state of interacting molecules contributes significantly to interactions of Ade with amino acids.