Barrier-free proton transfer in the valence anion of 2'-deoxyadenosine-5'-monophosphate. II. A computational study.
The propensity of four representative conformations of 2(')-deoxyadenosine-5(')-monophosphate (5(')-dAMPH) to bind an excess electron has been studied at the B3LYP6-31++G(d,p) level. While isolated canonical adenine does not support stable valence anions in the gas phase, all considered neutral conformations of 5(')-dAMPH form adiabatically stable anions. The type of an anionic 5(')-dAMPH state, i.e., the valence, dipole bound, or mixed (valence/dipole bound), depends on the internal hydrogen bond(s) pattern exhibited by a particular tautomer. The most stable anion results from an electron attachment to the neutral syn-south conformer. The formation of this anion is associated with a barrier-free proton transfer triggered by electron attachment and the internal rotation around the C4(')-C5(') bond. The adiabatic electron affinity of the a_south-syn anion is 1.19 eV, while its vertical detachment energy is 1.89 eV. Our results are compared with the photoelectron spectrum (PES) of 5(')-dAMPH(-) measured recently by Stokes et al., [J. Chem. Phys. 128, 044314 (2008)]. The computational VDE obtained for the most stable anionic structure matches well with the experimental electron binding energy region of maximum intensity. A further understanding of DNA damage might require experimental and computational studies on the systems in which purine nucleotides are engaged in hydrogen bonding.
Kobyłecka
Monika
M
Faculty of Chemistry, University of Gdańsk, 80-952 Gdańsk, Sobieskiego 18, Poland.
Gu
Jiande
J
Rak
Janusz
J
Leszczynski
Jerzy
J
D000465:Algorithms; D000838:Anions / Q000737:chemistry*; D003838:Deoxyadenine Nucleotides / Q000737:chemistry*; D004583:Electrons; D004735:Energy Transfer; D006860:Hydrogen Bonding; D008958:Models, Molecular; D011522:Protons
D000838:Anions; D003838:Deoxyadenine Nucleotides; D011522:Protons; C012873:2'-deoxy-5'-adenosine monophosphate