title: Excess Electron Attachment to the Nucleoside Pair 2'-Deoxyadenosine (dA)-2'-Deoxythymidine (dT).
abstract: The 2'-deoxyadenosine···2'-deoxythymidine (dAdT(•-)) radical anion nucleoside pair has been investigated both experimentally and theoretically in the gas phase. The vertical detachment energy (VDE) and adiabatic electron affinity (AEA) were determined by anion photoelectron spectroscopy (PES). The measured photoelectron spectrum features a broad band having an onset at ∼1.1 eV and a maximum at the electron binding energy (EBE) ranging from 1.7 to 1.9 eV. Calculations performed at the M06-2X/6-31++G** level reveal that the observed PES signal is probably due to a dAdT(•-) complex in which the thymine of the dT nucleoside forms hydrogen bonds that engage its O7 and O8 atoms as well as the 3'- and 5'-hydroxyl groups of 2'-deoxyadenosine (dA), while dT's 3'-hydroxyl group interacts with the N1 of dA. In this heterodimer, the excess electron is entirely located on thymine. The biologically relevant Watson-Crick arrangement of the dAdT(•-) dimer was found to be substantially less stable (by ∼19 kcal mol(-1) in Gibbs free energy scale) than the above-mentioned configuration; hence, it is not populated in the gas phase.
authors.affiliation: Faculty of Chemistry, University of Gdańsk , Wita Stwosza 63, 80-308 Gdańsk, Poland.
authors.forename: Piotr
authors.initials: P
authors.lastname: Storoniak
authors.affiliation: Faculty of Chemistry, University of Gdańsk , Wita Stwosza 63, 80-308 Gdańsk, Poland.
authors.forename: Janusz
authors.initials: J
authors.lastname: Rak
authors.affiliation: Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Yeon Jae
authors.initials: YJ
authors.lastname: Ko
authors.affiliation: Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Haopeng
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Chemistry, Johns Hopkins University , Baltimore, Maryland 21218, United States.
authors.forename: Kit H
authors.initials: KH
authors.lastname: Bowen
mesh_terms: D000838:Anions / Q000737:chemistry; D003839:Deoxyadenosines / Q000737:chemistry* / Q000378:metabolism; D019281:Dimerization; D004583:Electrons; D005609:Free Radicals / Q000737:chemistry; D006860:Hydrogen Bonding; D056951:Photoelectron Spectroscopy; D013816:Thermodynamics; D013936:Thymidine / Q000737:chemistry* / Q000378:metabolism
chemical_list: D000838:Anions; D003839:Deoxyadenosines; D005609:Free Radicals; C058118:2'-deoxyadenosine; D013936:Thymidine