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Capturing Transient Endoperoxide in the Singlet Oxygen Oxidation of Guanine
Author(s) -
Lu Wenchao,
Liu Jianbo
Publication year - 2016
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201504140
Subject(s) - guanine , singlet oxygen , chemistry , photochemistry , guanosine , singlet state , protonation , ion , oxygen , organic chemistry , excited state , atomic physics , nucleotide , biochemistry , physics , gene
The chemistry of singlet O 2 toward the guanine base of DNA is highly relevant to DNA lesion, mutation, cell death, and pathological conditions. This oxidative damage is initiated by the formation of a transient endoperoxide through the Diels–Alder cycloaddition of singlet O 2 to the guanine imidazole ring. However, no endoperoxide formation was directly detected in native guanine or guanosine, even at −100 °C. Herein, gas‐phase ion–molecule scattering mass spectrometry was utilized to capture unstable endoperoxides in the collisions of hydrated guanine ions (protonated or deprotonated) with singlet O 2 at ambient temperature. Corroborated by results from potential energy surface exploration, kinetic modeling, and dynamics simulations, various aspects of endoperoxide formation and transformation (including its dependence on guanine ionization and hydration states, as well as on collision energy) were determined. This work has pieced together reaction mechanisms, kinetics, and dynamics data concerning the early stage of singlet O 2 induced guanine oxidation, which is missing from conventional condensed‐phase studies.