RADICALS DERIVED FROM GUANINE: STRUCTURES AND ENERGETICS

摘要

The electron affinities (EA) of five radicals derived from guanine by removing a hydrogen atom are predicted by using four carefully calibrated (Chem.Rev.2002,102,231) density functional methods.The most stable guanine radical arises from the removal of the H~(10b) atom (Fig.1) from the NH_2 group.The theoretical adiabatic electron affinities (EA_(ad)) for the five possible guanine radicals are substantial,in the range of 2.18-2.99 eV,which is much higher than that for the closed-shell guanine molecule (-0.17 eV).The N9 dehydrogenated radical has the highest EA_(ad) (2.99 eV),and its related anion is the lowest energy species among those studied in the present research.The energy difference between the two N~(10)-sited (amino group) radicals is 4.8 kcal/mol,indicating that these two structures are not conventional internal-rotation conformers.