Probing the nature of hydrogen bonds in DNA base pairs

摘要: Energy decomposition analyses based on the block-localized wave-function (BLW-ED) method are conducted to explore nature of hydrogen bonds in DNA base pairs terms deformation, Heitler–London, polarization, electron-transfer and dispersion-energy terms, where Heitler–London energy term is composed electrostatic Pauli-exchange interactions. A modest effect found Watson–Crick adenine–thymine (AT), guanine–cytosine (GC) Hoogsteen adenine-thymine (H-AT) pairs, confirming weak covalence bonds. The attraction polarization effects account for most binding energies, particularly GC pair. Both theoretical experimental data show that pair has a (−25.4 kcal mol−1 at MP2/6-31G** level) twice AT (−12.4 kcal mol−1) H-AT (−12.8 kcal mol−1) compared with three conventional N-H···O(N) two or Although remarkably strong between guanine cytosine bases benefits from opposite orientations dipole moments these assisted by π-electron delocalization amine groups carbonyl groups, model calculations demonstrate π-resonance very limited influence Thus, often adopted terminology “resonance-assisted bonding (RHAB)” may be replaced binding” which highlights rather than enhanced stabilization, as usually regarded covalent