title: Photoinduced Electron Transfer in DNA: Charge Shift Dynamics Between 8-Oxo-Guanine Anion and Adenine.
abstract: Femtosecond time-resolved IR spectroscopy is used to investigate the excited-state dynamics of a dinucleotide containing an 8-oxoguanine anion at the 5'-end and neutral adenine at the 3'-end. UV excitation of the dinucleotide transfers an electron from deprotonated 8-oxoguanine to its π-stacked neighbor adenine in less than 1 ps, generating a neutral 8-oxoguanine radical and an adenine radical anion. These species are identified by the excellent agreement between the experimental and calculated IR difference spectra. The quantum efficiency of this ultrafast charge shift reaction approaches unity. Back electron transfer from the adenine radical anion to the 8-oxguanine neutral radical occurs in 9 ps, or approximately 6 times faster than between the adenine radical anion and the 8-oxoguanine radical cation (Zhang, Y. et al. Proc. Natl. Acad. Sci. U.S.A. 2014, 111, 11612-11617). The large asymmetry in forward and back electron transfer rates is fully rationalized by semiclassical nonadiabatic electron transfer theory. Forward electron transfer is ultrafast because the driving force is nearly equal to the reorganization energy, which is estimated to lie between 1 and 2 eV. Back electron transfer is highly exergonic and takes place much more slowly in the Marcus inverted region.
authors: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
authors: Yuyuan
authors: Y
authors: Zhang
authors: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
authors: Jordan
authors: J
authors: Dood
authors: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
authors: Ashley A
authors: AA
authors: Beckstead
authors: ‡Department of Chemistry, University of Utah, 315 S. 1400 East, Salt Lake City, Utah 84112, United States.
authors: Xi-Bo
authors: XB
authors: Li
authors: ‡Department of Chemistry, University of Utah, 315 S. 1400 East, Salt Lake City, Utah 84112, United States.
authors: Khiem V
authors: KV
authors: Nguyen
authors: ‡Department of Chemistry, University of Utah, 315 S. 1400 East, Salt Lake City, Utah 84112, United States.
authors: Cynthia J
authors: CJ
authors: Burrows
authors: §CNR-Consiglio Nazionale delle Ricerche Istituto di Biostrutture e Bioimmagini (IBB-CNR), Via Mezzocannone 16, 80136 Napoli, Italy.
authors: Roberto
authors: R
authors: Improta
authors: †Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States.
authors: Bern
authors: B
authors: Kohler
mesh_terms: D000225:Adenine / Q000737:chemistry*; D000838:Anions / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D004579:Electron Transport; D006151:Guanosine / Q000031:analogs & derivatives* / Q000737:chemistry; D055668:Photochemical Processes; D011789:Quantum Theory
chemical_list: D000838:Anions; D006151:Guanosine; C046215:8-hydroxyguanosine; D004247:DNA; D000225:Adenine