Marked influences on the adenine-cytosine base pairs by electron attachment and ionization.
The reverse wobble and the reverse Hoogsteen adenine-cytosine mispairs regarding their radical cations and anions are studied with the hybrid three-parameter B3LYP density functional method and 6-31+G(d), 6-311+G(2df,2p) basis sets. Hydrogen bonding mispairs are remarkably influenced by electron attachment and ionization. Only one stronger hydrogen bond N6-H (in adenine)...N3 (in cytosine) exists in the radical pair, while the strengths of two N-H...N hydrogen bonds in the neutral pair are comparable. Geometrical coplanarity is found for the neutral and cationic pairs, in contrast to the anionic pairs in which the cytosine moiety exhibits significant deformation due to electron attachment. Dissociation energies for the neutral and radical pairs are slightly higher than those of the adenine-thymine pairs but much smaller than those of the guanine-cytosine pairs. Valence-bound anions of these two adenine-cytosine pairs are thermodynamically stable by 0.1-0.2 eV with respect to the neutral pairs. On the basis of the comparison between the experimental data of the solvated clusters and the calculated values, these two pairs can be quantitatively equivalent to the clusters in which each base is solvated by five water molecules.
Tian
Shan Xi
SX
Hefei National Laboratory for Physical Sciences at Microscale, Laboratory of Bond Selective Chemistry, Department of Chemical Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China. sxtian@ustc.edu.cn
D000225:Adenine / Q000737:chemistry*; D020029:Base Pairing; D003596:Cytosine / Q000737:chemistry*; D004583:Electrons; D006860:Hydrogen Bonding; D007477:Ions; D008958:Models, Molecular
D007477:Ions; D003596:Cytosine; D000225:Adenine