In this work, we have performed quantum chemical calculations on a new form of the guanine-cytosine anion, in which the excess electron is suspended between the two systems. The vertical detachment energy calculations performed with the MP2 method yield a value of 0.40 eV, showing a stability relative to the addition of this excess electron. The effects of removing the excess electron are also presented, whereby a significant change in the structure occurs. In these geometry optimizations of the neutral structure initiated with geometry of the anion, we obtain a hydrogen-bonded dimer with energy lower than the anion. (c) 2005 Published by Elsevier B.V.