Characterizing radiation-induced oxidation of DNA by way of the monohydrated guanine-cytosine radical cation.
The interaction of one water molecule with the guanine-cytosine radical cation has been studied with ab initio and density functional methods in order to help elucidate the nature of oxidized aqueous DNA. The theoretical spin density of [GC]*(+) reveals that the radical center is localized on guanine. The adiabatic ionization potential lowers from 7.63 to 6.71 eV in concurrence with the formation of the Watson-Crick base pair and hydration by one water molecule. A natural bond orbital analysis of partial charges shows that approximately 80% of the positive charge persists on guanine upon hydration and formation of the Watson-Crick base pair with cytosine. Hydration energies were computed with second-order Z-averaged perturbation theory (ZAPT2) using the aug-cc-pVDZ basis set at 11 stationary points on the B3LYP/DZP++ potential energy surface. The hydration energy at the global minimum is 14.2 kcal mol(-1). The lowest energy structures correspond to hydration near the glycosidic bond sites. Structural changes in the Watson-Crick base pair are predominantly seen for monohydration in the groove regions of double-helix DNA.
Jaeger
Heather M
HM
Center for Computational Quantum Chemistry, University of Georgia, Athens, Georgia 30602-2556, USA. jaeger@ccqc.uga.edu
Schaefer
Henry F
HF
D003596:Cytosine / Q000737:chemistry*; D004249:DNA Damage; D006147:Guanine / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D055672:Static Electricity
D006147:Guanine; D003596:Cytosine