Proton-coupled electron transfer in the oxidation of guanines by an aromatic pyrenyl radical cation in aqueous solutions

Vladimir A. Kuzmin, Alexander Dourandin, Vladimir Shafirovich, Nicholas Geacintov

Research output: Contribution to journalArticle

Abstract

Electron transfer reactions between nucleic acid residues in DNA and strong oxidants are often the critical initial steps that initiate oxidative, irreversible DNA damage. Employing laser flash photolysis transient absorption spectroscopic techniques, we investigated the characteristics of electron transfer reactions in aqueous solutions between the 2'- deoxynucleoside 5'-monophosphates, dGMP, dAMP, dCMP and dTMP and a representative one-electron oxidant. The latter was a radical cation of a pyrene derivative with enhanced water-solubility, 7,8,9,10- tetrahydroxytetrahydrobenzo[a]pyrene (BPT). The BPT radical cation BPT+, was generated by intense nanosecond laser pulse (308 or 355 nm, 50-70 mJ pulse-1 cm-2) by a non-linear consecutive two-photon absorption process. No electron transfer reactions were observed with dAMP, dTMP and dCMP, consistent with their unfavorable redox potentials. However, BPT+ efficiently oxidized dGMP with a rate constant k(b) = 1.7 ± 0.1) x 109 M-1 s-1, which is smaller than the diffusion-controlled value by a factor of only ~ 3. The dGMP(-H) neutral radicals formed on time scales of a few microseconds, were identified by their characteristic transient absorption spectrum (λ(max) ~ 310 mn). The rate constant of electron transfer from dGMP to BPT+ was smaller in D2O by a factor of ~ 1.5 than in H2O. This kinetic isotope effect indicates that the electron transfer reaction from dGMP to BPT+ is accompanied by the deprotonation of dGMP+, and therefore appears to be a proton-coupled electron transfer reaction.

Original languageEnglish (US)
Pages (from-to)1531-1535
Number of pages5
JournalPhysical Chemistry Chemical Physics
Volume2
Issue number7
DOIs
StatePublished - Apr 1 2000

Fingerprint

guanines
Guanine
Cations
Protons
electron transfer
aqueous solutions
cations
Oxidation
oxidation
protons
Electrons
pyrenes
Oxidants
deoxyribonucleic acid
Rate constants
nucleic acids
Deprotonation
pulses
DNA
Photolysis

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Atomic and Molecular Physics, and Optics

Cite this

Proton-coupled electron transfer in the oxidation of guanines by an aromatic pyrenyl radical cation in aqueous solutions. / Kuzmin, Vladimir A.; Dourandin, Alexander; Shafirovich, Vladimir; Geacintov, Nicholas.

In: Physical Chemistry Chemical Physics, Vol. 2, No. 7, 01.04.2000, p. 1531-1535.

Research output: Contribution to journalArticle

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