The influence of Cu + binding to hypoxanthine on stabilization of mismatches involving hypoxanthine and DNA bases: A DFT study.

In the present work, the influence of Cu+ binding to N3- and N7-positions of hypoxanthine on energetic, geometrical and topological properties of hypoxanthine-guanine, hypoxanthine-adenine, hypoxanthine-cytosine, hypoxanthine-thymine and hypoxanthine-hypoxanthine mismatches is theoretically investigated. The calculations, in gas phase, are performed at B3LYP/6-311++G(3df,3pd) level of theory. Unlike the other mispairs, Cu+ binding to N3-position of hypoxanthine causes the proton transfer process from enol form of hypoxanthine to imino forms of adenine and cytosine. This process also occurs in all mismatches having enol form of hypoxanthine when Cu+ binds to N7-position of hypoxanthine. The mismatches are stabilized by hydrogen bonds. The influence of Cu+ on hydrogen bonds is also examined by atoms in molecules (AIM) and natural bond orbital (NBO) analyses.