Kinetics of the Oxidation of Thymine and Thymidine by Triplet 2,2′-Dipyridyl in Aqueous Solutions at Different pH Values

Abstract

The photo-oxidation of the nucleobase, thymine (Thy), and nucleoside, thymidine (dThy), by dipyridyl (DP) has been investigated in aqueous solution using time-resolved laser flash photolysis. The pH dependence of the oxidation rate constants is measured within a large pH scale. As a consequence, the chemical reactivity of the reactants existing in solution at a certain range of pH is predicted. Bimolecular rate constants of the quenching reactions between triplet dipyridyl and thymine and thymidine are, respectively, kq = 2.4 × 107 M–1 s–1 (pH < 5.8) and kq = 1.0 × 107 M–1 s–1 (5.8 < pH < 9.8). Cyclic voltammetry was used to measure the potentials of thymine oxidation and dipyridyl reduction in water at pH < 7. Both results give hints for a proton coupled electron-transfer (PCET) reaction from thymine to triplet dipyridyl.

Maclurin protects against hydroxyl radical-induced damages to mesenchymal stem cells: Antioxidant evaluation and mechanistic insight

“…It means that maclurin could effectively scavenge ABTS +Å through e transfer. The e transfer however is always accompanied by deprotonation, so it is usually termed SEPT [41], or equential proton loss single electron transfer (SPLET) [14], proton coupled electron-transfer (PCET) [42]. The SEPT mechanism for maclurin to scavenge ABTS +Å is proposed as described in Fig.…”

Quantum‐Chemical Studies to Approach the Antioxidant Mechanism of Nonphenolic Hydrazone Schiff Base Analogs: Synthesis, Molecular Structure, Hirshfeld and Density Functional Theory Analyses

“…The antioxidant mechanism of phenolics are well documented and involve processes, such as, hydrogen atom transfer (HAT), protoncoupled electron transfer (PCET), electron transfer-proton transfer (ET-PT), sequential proton loss single electron transfer (SPLET), sequential electron-proton transfer (SEPT), and adduct formation. [16][17][18][19][20] For this reason, it is also important to determine mechanisms responsible for the activities of nonphenolic antioxidants with the aims of improving potency and discovering new antioxidant agents to fight against the fatal diseases caused by free radicals. In the present study, we report the antioxidant mechanism of nonphenolic (E)-N 0 -benzylidenebenzohydrazide analogs together with the synthesis, crystal structure, and Hirshfeld analyses.…”