In (a) the evolution of the distances (in A) from oxygen atom in the OH radical to the HN1 in the spin singlet guanine in vacuum (filled red circles), in solution (open black circles), and in the spin triplet in solution (blue stars) are shown. The hydrogen abstraction for singlet guanine in vacuum and solution occurs around t ≈ 0.07 and t ≈ 0.12 ps, respectively, and it does not occur for triplet guanine in solution. In (b) and (c) the evolution of the angle between HN1 and OH radical in the spin singlet guanine in vacuum (filled red circles) and in solution (open black circles) are shown. The horizontal dashed line shows the angle 109.5 degrees. The vertical lines show the expected position of Hydrogen abstraction, consistent with the distance-time calculation shown in (a).