title: Electron interaction with a DNA duplex: dCpdC:dGpdG.
abstract: Electron attachment to double-stranded cytosine-rich DNA, dCpdC:dGpdG, has been studied by density functional theory. This system represents a minimal descriptive unit of a cytosine-rich double-stranded DNA helix. A significant electron affinity for the formation of a cytosine-centered radical anion is revealed to be about 2.2 eV. The excess electron may reside on the nucleobase at the 5' position (dC˙(-)pdC:dGpdG) or at the 3' position (dCpdC˙(-):dGpdG). The inter-strand proton transfer between the radical anion centered cytosine (N3) and the paired guanine (HN1) results in the formation of radical anion center separated complexes dC1H˙pdC:dG2-H(-)pdG and dCpdC2H˙:dGpdG1-H(-). These distonic radical anions are found to be approximately 1 to 4 kcal mol(-1) more stable than the normal radical anions. Intra-strand cytosine π→π transition energies are below the electron detachment energy. Inter-strand π→π transitions of the excess electron from C to G are predicted to be less than 2.79 eV. Electron transfer might also be possible through the inter-strand base-jumping mode. An analysis of absorption visible spectra reveals the absorption bands ranging from 500 nm to 700 nm for the cytosine-rich radical anions of the DNA duplex. Electron attachment to cytidine oligomers might add color to the DNA duplex.
authors.affiliation: Drug Design & Discovery Center, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China. jiande@icnanotox.org.
authors.forename: Jiande
authors.initials: J
authors.lastname: Gu
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.forename: Jerzy
authors.initials: J
authors.lastname: Leszczynski
mesh_terms: D020029:Base Pairing; D003596:Cytosine / Q000737:chemistry*; D004247:DNA / Q000737:chemistry*; D015226:Dinucleoside Phosphates / Q000737:chemistry*; D004583:Electrons; D006147:Guanine / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D015394:Molecular Structure; D009838:Oligodeoxyribonucleotides / Q000737:chemistry*; D011522:Protons; D011789:Quantum Theory
chemical_list: D015226:Dinucleoside Phosphates; D009838:Oligodeoxyribonucleotides; D011522:Protons; C034298:deoxyguanylyl-(3'-5')-guanosine; D006147:Guanine; D003596:Cytosine; D004247:DNA