THEORETICAL STUDY OF THE STRUCTURAL AND ENERGETICS PROPERTIES OF THE INTERACTION SIDES OF GUANINE AND ADENINE IN GG AND AA TRANS BASE PAIRS

In the present work we have carried out an ab initio study on the structural and energetic properties of the hydrogen bonding formed between the different interaction sides of Guanine (G) and Adenine (A) in the GG and AA trans non Watson-Crick base pairs. The energies derived at the HF/6-31G(d,p) level, show that while Watson-Crick sides contribute significantly to the stabilization of the hydrogen bonding, however, Sugar and Hoogsteen sides interacciones are weaker. The inclusion of electronic correlation at the second order M0ller- Plesset perturbation method, confirm the importance of including this correlation at MP2/6-31G(d,p) and MP2/6-311G(d,p) levels. It is concluded that two Guanine molecules form hydrogen bonds energetically more favorable than AA pairs within the same kind of interaction, while those having the sugar-sugar GG interaction become better solvated in aqueous solution. The results also allow understanding the functional role of this type of interaction in the oligonucleotide.