Interactions of adenine, thymine, and uracil with epinephrine: UV studies

Based upon UV absorption studies, charge transfer complex formations by the nucleic acid bases adenine, thymine, and uracil with epinephrine were demonstrated. The pertient equilibrium constants were calculated by assuming 1:1 complexes using the Benesi-Hildebrand equation and were found to decrease in the following order: uracil-epinephrine greater than thymine-epinephrine greater than adenine-epinephrine. The values of delta G degrees, delta H degrees, and delta S degrees were calculated for the various interactions. Theoretical arguments are presented as to the possible stoichiometries of the various complexes existing in aqueous solutions. The electron-donating or electron-accepting abilities of the interacting molecular species are discussed.