Density functional theory reveals an increase in the amino 1H chemical shift in guanine due to hydrogen bonding with water

Electronic structure calculations underestimate the chemical shift of the non H-bonded amino proton (1)H22 in isolated G-quartet structures. The current work shows that this underestimation is due to the absence of a water environment in the calculations: coordination of at least two water molecules is required to obtain good agreement with experiment. The results indicate how improved agreement between calculated and experimental (solution-phase) NMR data can be obtained. (c) 2006 American Institute of Physics.