THEORETICAL STUDY OF THE NON-WATSON-CRICK BASE PAIR GUANINE-GUANINE

Abstract

ABSTRACT A theoretical study of the non canonical base pair, Guanine-Guanine (G-G) has been carried out in the frame of molecular orbital theory using density functional theory (DFT). The Becke three parameter hybrid including correlation functional that contains local and non-local terms (B3LYP) was used thoroughly. The 6-31G(d,p) basis set was employed to obtain the optimized geometry and energy of the non-Watson-Crick pair formed between two molecules of guanine. The results compare well with the properties of other base pairs of biological interest. At the DFT level the non-planarity of the pair is evident. The two guanines molecules are bent by ca 12 o and buckled. The interaction energy corrected by BSSE is equal to -10.7 kcal / mol, similar to that calculated for other pairs involving bases of nucleic acids. INTRODUCTION The interaction between nitrogen bases of nucleic acids is a molecular recognition event that has been widely studied 1-4 . The interaction takes place trough extensive hydrogen bonding leading to the canonical pairs: guanine-cytosine (G-C), adenine-thymine (A-T) and adenine-uracile (A-U). A base pairing occurring in any other combinations but these given above, conduct to a non-canonical pair formation.