On the Stability of Uracil-Glycine Hydrogen-Bonded Complexes. A Computational Study

The topological space of the glycine-uracil complex has been scanned at the semiempirical PM3 level of theory and the lowest energy complexes have been characterized at the B3LYP/6-31++G** level. These complexes are characterized by two hydrogen bonds, in which the carboxylic group of glycine interacts with proton donor and acceptor sites of uracil. The stabilization energy for three complexes, with the NH___O and O___HO hydrogen bonds each, spans a narrow range of 15.6-12.3 kcal/mol. The fourth complex with one strongO___HOand one weakCH___Ohydrogen bond is bound by 10.2 kcal/mol.