ElectronInteraction with Phosphate Cytidine OligomerdCpdC: Base-Centered Radical Anions and Their Electronic Spectra.

Computationalchemistry approach was applied to explore the natureof electron attachment to cytosine-rich DNA single strands. An oligomerdinucleoside phosphate deoxycytidylyl-3′,5′-deoxycytidine(dCpdC) was selected as a model system for investigations by densityfunctional theory. Electron distribution patterns for the radicalanions of dCpdC in aqueous solution were explored. The excess electronmay reside on the nucleobase at the 5′ position (dC•–pdC) or at the 3′ position (dCpdC•–). From comparison with electron attachment to the cytosine relatedDNA fragments, the electron affinity for the formation of the cytosine-centeredradical anion in DNA is estimated to be around 2.2 eV. Electron attachmentto cytosine sites in DNA single strands might cause perturbationsof local structural characteristics. Visible absorption spectroscopymay be applied to validate computational results and determine experimentallythe existence of the base-centered radical anion. The time-dependentDFT study shows the absorption around 550–600 nm for the cytosine-centeredradical anions of DNA oligomers. This indicates that if such speciesare detected experimentally they would be characterized by a distinctivecolor. [ABSTRACT FROM AUTHOR]