Spectroscopic probe on N-H⋯N, N-H⋯O and controversial C-H⋯O contact in A-T base pair: a DFT study.

DNA base pair A-T has been investigated by IR and NMR spectroscopy using DFT methods. The results have been analyzed in terms of infrared vibrational frequencies and (1)H NMR chemical shifts. Different types of interactions N-H⋯N, N-H⋯O and C-H⋯O types have been investigated in DNA base pairs. Although, previous reports argued about the third C-H⋯O type interaction in A-T base pair, such typical interaction has been analyzed thoroughly by IR and NMR spectroscopy using DFT methods. Our results show that the CH⋯O interaction in the A-T base pair is a weak interaction compared to normal hydrogen bond interactions.