| Autor: |
Skotnicki K; Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, 03-195 Warsaw, Poland., Taras-Goslinska K; Faculty of Chemistry, Adam Mickiewicz University, 61-614 Poznan, Poland., Janik I; Notre Dame Radiation Laboratory, University of Notre Dame, Notre Dame, IN 46556, USA., Bobrowski K; Centre of Radiation Research and Technology, Institute of Nuclear Chemistry and Technology, 03-195 Warsaw, Poland. |
| Jazyk: |
angličtina |
| Zdroj: |
Molecules (Basel, Switzerland) [Molecules] 2019 Dec 02; Vol. 24 (23). Date of Electronic Publication: 2019 Dec 02. |
| DOI: |
10.3390/molecules24234402 |
| Abstrakt: |
Oxidative damage to 2-thiouracil (2-TU) by hydroxyl ( • OH) and azide ( ● N 3 ) radicals produces various primary reactive intermediates. Their optical absorption spectra and kinetic characteristics were studied by pulse radiolysis with UV-vis spectrophotometric and conductivity detection and by time-dependent density functional theory (TD-DFT) method. The transient absorption spectra recorded in the reactions of • OH with 2-TU depend on the concentration of 2-TU, however, only slightly on pH. At low concentrations, they are characterized by a broad absorption band with a weakly pronounced maxima located at λ = 325, 340 and 385 nm, whereas for high concentrations, they are dominated by an absorption band with λ max ≈ 425 nm. Based on calculations using TD-DFT method, the transient absorption spectra at low concentration of 2-TU were assigned to the ● OH-adducts to the double bond at C5 and C6 carbon atoms (3 ● , 4 ● ) and 2c-3e bonded ● OH adduct to sulfur atom (1… ● OH) and at high concentration of 2-TU also to the dimeric 2c-3e S-S-bonded radical in neutral form (2 ● ). The dimeric radical (2 ● ) is formed in the reaction of thiyl-type radical (6 ● ) with 2-TU and both radicals are in an equilibrium with K eq = 4.2 × 10 3 M -1 . Similar equilibrium (with K eq = 4.3 × 10 3 M -1 ) was found for pH above the pK a of 2-TU which involves admittedly the same radical (6 ● ) but with the dimeric 2c-3e S-S bonded radical in anionic form (2 ●- ). In turn, ● N 3 -induced oxidation of 2-TU occurs via radical cation with maximum spin location on the sulfur atom which subsequently undergoes deprotonation at N1 atom leading again to thiyl-type radical (6 ● ). This radical is a direct precursor of dimeric radical (2 ● ). |
| Databáze: |
MEDLINE |
| Externí odkaz: |
|
|
Nepřihlášeným uživatelům se plný text nezobrazuje |
K zobrazení výsledku je třeba se přihlásit.
|
