title: UV-Induced Proton-Coupled Electron Transfer in Cyclic DNA Miniduplexes.
abstract: The excited-state dynamics of two cyclic DNA miniduplexes, each containing just two base pairs, are investigated using time-resolved infrared spectroscopy. As in longer DNA duplexes, intrastrand electron transfer induced by UV excitation triggers interstrand proton transfer in the alternating miniduplex containing two out-of-phase G·C base pairs. The resulting excited state decays on a time scale of several tens of picoseconds. This state is absent when one of the two G residues is substituted by 8-oxo-7,8-dihydroguanine, a modification that is suggested to disrupt base stacking, while maintaining base pairing. These findings demonstrate that a nucleobase tetramer arranged as two stacked base pairs accurately captures the interplay between intrastrand and interstrand decay channels. The similar signals seen in the miniduplexes and longer sequences suggest that excited states in the latter rapidly localize on two adjacent base pairs.
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.
authors.forename: Yuyuan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112, United States.
authors.forename: Xi-Bo
authors.initials: XB
authors.lastname: Li
authors.affiliation: Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112, United States.
authors.forename: Aaron M
authors.initials: AM
authors.lastname: Fleming
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.
authors.forename: Jordan
authors.initials: J
authors.lastname: Dood
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.
authors.forename: Ashley A
authors.initials: AA
authors.lastname: Beckstead
authors.affiliation: Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112, United States.|Center for High Performance Computing, University of Utah , Salt Lake City, Utah 84112-0190, United States.
authors.forename: Anita M
authors.initials: AM
authors.lastname: Orendt
authors.affiliation: Department of Chemistry, University of Utah , 315 S. 1400 East, Salt Lake City, Utah 84112, United States.
authors.forename: Cynthia J
authors.initials: CJ
authors.lastname: Burrows
authors.affiliation: Department of Chemistry and Biochemistry, Montana State University , Bozeman, Montana 59717, United States.
authors.forename: Bern
authors.initials: B
authors.lastname: Kohler
mesh_terms: D020029:Base Pairing; D003500:Cyclization; D004247:DNA / Q000737:chemistry*; D004579:Electron Transport; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry; D009690:Nucleic Acid Conformation; D011522:Protons; D014466:Ultraviolet Rays
chemical_list: D011522:Protons; C024829:8-hydroxyguanine; D006147:Guanine; D004247:DNA