Journal
CHEMISTRY-A EUROPEAN JOURNAL
Volume 16, Issue 17, Pages 5089-5096Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.200902977
Keywords
density functional calculations; DNA; electron affinity; oligonucleotides; radical ions
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Funding
- U.S. National Science Foundation [CHE-0749868]
- Chinese Academy of Sciences
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The dinucleoside phosphate deoxycytidylyl-3',5'-deoxyguanosine (dCpdG) and deoxyguanylyl-3',5'-deoxycytidine (dGpdC) systems are among the largest to be studied by reliable theoretical methods. Exploring electron attachment to these subunits of DNA single strands provides significant progress toward definitive predictions of the electron affinities of DNA single strands. The adiabatic electron affinities of the oligonucleotides are found to be sequence dependent. Deoxycytidine (dC) on the 5' end, dCpdG, has larger adiabatic electron affinity (AEA, 0.90 eV) than dC on the 3' end of the oligomer (dGpdC, 0.66 eV). The geometric features, molecular orbital analyses, and charge distribution studies for the radical anions of the cytidine-containing oligonucleotides demonstrate that the excess electron in these anionic systems is dominantly located on the cytosine nucleobase moiety. The sr-stacking interaction between nucleobases G and C seems unlikely to improve the electron-capturing ability of the oligonucleotide dimers. The influence of the neighbor- ing base on the electron-capturing ability of cytosine should be attributed to the intensified proton accepting donating interaction between the bases. The present investigation demonstrates that the vertical detachment energies (VDEs) of the radical anions of the oligonucleotides dGpdC and dCpdG are significantly larger than those of the corresponding nucleotides. Consequently, reactions with low activation barriers, such as those for O-C sigma bond and N-glycosidic bond breakage, might be expected for the radical anions of the guanosine cytosine mixed oligonucleotides.
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