The Elusive Noncanonical Isomers of Ionized 9-Methyladenine and 2'-Deoxyadenosine

0541226 - ÚOCHB 2022 RIV US eng J - Článek v odborném periodiku
Huang, S. R. - Nováková, Gabriela - Marek, Aleš - Tureček, F.
The Elusive Noncanonical Isomers of Ionized 9-Methyladenine and 2'-Deoxyadenosine.
Journal of Physical Chemistry A. Roč. 125, č. 1 (2021), s. 338-348. ISSN 1089-5639. E-ISSN 1520-5215
Grant CEP: GA MŠMT(CZ) LTAUSA19094
Institucionální podpora: RVO:61388963
Klíčová slova: photodissociation action spectroscopy * distonic radical cations * basis-set convergence
Obor OECD: Physical chemistry
Impakt faktor: 2.944, rok: 2021
Způsob publikování: Omezený přístup
https://doi.org/10.1021/acs.jpca.0c10293

Noncanonical nucleobases and nucleosides represent newly discovered species of relevance for DNA ionization. We report a targeted synthesis of gas-phase 9-methylene(1H)adenine cation radical (2(+center dot)) as a low-energy isomer of ionized 9-methyladenine. Ion 2(+center dot) showed unique collision-induced dissociation and UV-vis photodissociation action spectra that distinguished it from other cation radical isomers. Ab initio energy calculations with coupled cluster theory extrapolated to the complete basis set limit, CCSD(T)/CBS, identified cation radical 2(+center dot) as the global energy minimum of the adenine-related C6H7N5+center dot isomers. The action spectrum of 2(+center dot) was assigned on the basis of vibronic absorption spectra that were calculated with time-dependent density functional theory for multiple vibrational configurations of thermal ions. The major dissociation of 2(+center dot) proceeded by hydrogen loss that was elucidated by deuterium labeling at the exchangeable N-1 and NH2 positions and C-8 position and by kinetic analysis. The dissociation involved a reversible rearrangement to intermediate dihydropteridine structures, yielding a protonated aminopteridine as the product, which was identified by multistep UV-vis action spectroscopy. We also report a computational study of related noncanonical isomers of 2'-deoxyadenosine cation radical having the radical defect at C-1' that were found to be thermodynamically more stable than the canonical isomer in both the gas phase and aqueous solution. The noncanonical isomers were calculated to have extremely low ion-electron recombination energies of 4.42-5.10 eV that would make them dead-end hole traps if produced by DNA ionization.
Trvalý link: http://hdl.handle.net/11104/0318815