Hydrogen-bonding interaction of 5,6-dihydrouracil with RNA bases: DFT and MP2 studies

5,6-Dihydrouracil (DHU) is a rare pyrimidine base naturally occurring in tRNAs, it differs from the base uracil due to the saturation of the C5-C6 bond. This work presents the interaction energies of complexes formation involving DHU bound to the natural RNA bases adenine (A), uracil (U), guanine (G), and cytosine (C). Full geometry optimization has been performed for the studied complexes by B3LYP/6-31+G(d,p) and MP2/6-31+G(d,p) calculations. The interaction energies were corrected for the basis-set superposition error (BSSE), using the full Boys-Bernardi counterpoise correction scheme. We find that the stability order is DHU:G > DHU:A > DHU:C ∼ DHU:U.