Theoretical study about remarkable stability of guanine tetramer

: The cyclic guanine tetramer (G-quartet) formation was theoretically studied. Total hydrogen bond energy in a G-quartet was large (-70.89 kcal/mol). though the hydrogen bond energy in Hoogsteen type guanine dimer was small (-11.26 kcal/mol). A large attractive interaction (-57.84 kcal/mol) was observed for stacking interaction. The hydration effect should be considered to explain the selectivity of metal incorporation into the G-quartet.