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{One-Electron Reduction of 8-Bromo-2-aminoadenosine in the Aqueous Phase: Radiation Chemical and DFT Studies of the Mechanism}

Citation:

Kaloudis P, D'Angelantonio M, Guerra M, Gimisis T, Mulazzani QG, Chatgilialoglu C. {One-Electron Reduction of 8-Bromo-2-aminoadenosine in the Aqueous Phase: Radiation Chemical and DFT Studies of the Mechanism}. J. Phys. Chem. B [Internet]. 2008;112:5209–5217.

Abstract:

Two tautomeric forms of one-electron oxidized 2-aminoadenosine (2AA) have been produced by reactions of hydrated electrons (eaq-) with 8-bromo-2-aminoadenosine (8-Br-2AA) at natural pH, whereas only one tautomer is formed by oxidation of 2AA. Tailored experiments by pulse radiolysis and time-dependent DFT (TD-B3LYP/6-311G**//B1B95/6-31+G**) calculations allowed the definition of the reaction mechanism in some detail. The electron adducts of 8-Br-2AA protonated at C8 eject Br- and produce the two short-lived tautomers (8 and 9). The first observable species decays by first-order kinetics to produce the second intermediate, which is also obtained by oxidation of 2AA by SO4•-. The rate of tautomerization (ktaut = 4.5 × 104 s -1) is strongly accelerated by phosphate and is retarded in D 2O (kinetic isotope effect 7). B1B95/6-31+G** calculations showed that the tautomerization is a water-assisted process. In acidic or basic solutions, the "instantaneous" formation of one-electron oxidized 2AA or its deprotonated forms has been produced by reactions of eaq- with 8-Br-2AA. $\gamma$-Radiolysis of 8-Br-2AA in aqueous solutions followed by product studies led to the formation of 2AA as a single product. © 2008 American Chemical Society.

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