title: Intrinsic lifetimes of the excited state of DNA and RNA bases.
abstract: The lifetimes of the excited state of free nucleobases were measured in the gas phase for the first time. They are, respectively, 1.0 and 0.8 ps for the purine bases adenine (shown above) and guanine and 3.2, 2.4, and 6.4 ps for the pyrimidine bases cytosine, uracil, and thymine at 267 nm. The longer lifetimes of the pyrimidine bases may be associated with their higher propensity toward photodegradation, especially in the case of thymine. The ultrashort lifetime of nucleobases conventionally known in solution was found to be an intrinsic molecular property due to extremely facile internal conversion, and therefore the lifetime should be largely independent of the medium at this energy, that is, whether in vacuo, in solution, or in vivo. The evolutionary selection of nucleobases as the durable carriers of genetic information is suggested to be due to their inherent immunity from photochemical reactions.
authors.affiliation: School of Chemistry, Seoul National University, Seoul 151-747, Korea.
authors.forename: Hyuk
authors.initials: H
authors.lastname: Kang
authors.forename: Kang Taek
authors.initials: KT
authors.lastname: Lee
authors.forename: Boyong
authors.initials: B
authors.lastname: Jung
authors.forename: Yeon Jae
authors.initials: YJ
authors.lastname: Ko
authors.forename: Seong Keun
authors.initials: SK
authors.lastname: Kim
mesh_terms: D000225:Adenine / Q000737:chemistry; D004247:DNA / Q000737:chemistry* / Q000528:radiation effects; D007834:Lasers; D012313:RNA / Q000737:chemistry* / Q000528:radiation effects; D013057:Spectrum Analysis / Q000379:methods
chemical_list: D012313:RNA; D004247:DNA; D000225:Adenine