title: Subnanosecond Emission Dynamics of AT DNA Oligonucleotides.
abstract: UV radiation creates excited electronic states in DNA that can decay to mutagenic photoproducts. When excited states return to the electronic ground state, photochemical injury is avoided. Understanding of the available relaxation pathways has advanced rapidly during the past decade, but there has been persistent uncertainty, and even controversy, over how to compare results from transient absorption and time-resolved emission experiments. Here, emission from single- and double-stranded AT DNA compounds excited at 265 nm was studied in aqueous solution using the time-correlated single photon counting technique. There is quantitative agreement between the emission lifetimes ranging from 50 to 200 ps and ones measured in transient absorption experiments, demonstrating that both techniques probe the same excited states. The results indicate that excitations with lifetimes of more than a few picoseconds are weakly emissive excimer and charge transfer states. Only a minute fraction of excitations persist beyond 1 ns in AT DNA strands at room temperature.
authors: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717-3400, USA.
authors: David J
authors: DJ
authors: Skowron
authors: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717-3400, USA.
authors: Yuyuan
authors: Y
authors: Zhang
authors: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717-3400, USA.
authors: Ashley A
authors: AA
authors: Beckstead
authors: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717-3400, USA.
authors: Jacob M
authors: JM
authors: Remington
authors: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717-3400, USA.
authors: Madison
authors: M
authors: Strawn
authors: Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717-3400, USA.
authors: Bern
authors: http://orcid.org/0000-0001-5353-1655
authors: B
authors: Kohler
mesh_terms: D004247:DNA / Q000737:chemistry*; D009841:Oligonucleotides / Q000737:chemistry*; D013816:Thermodynamics; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D009841:Oligonucleotides; D004247:DNA
keywords: DNA; charge transfer; fluorescence spectroscopy; photophysics; time-resolved spectroscopy