Generation of 8-oxo-7,8-dihydroguanine in G-Quadruplexes Models of Human Telomere Sequences by One-electron Oxidation

Tomasz J. Merta, Nicholas Geacintov, Vladimir Shafirovich

Research output: Contribution to journalArticle

Abstract

The mechanistic aspects of one-electron oxidation of G-quadruplexes in the basket (Na+ ions) and hybrid (K+ ions) conformations were investigated by transient absorption laser kinetic spectroscopy and HPLC detection of the 8-oxo-7,8-dihydroguanine (8-oxoG) oxidation product. The photo-induced one-electron abstraction from G-quadruplexes was initiated by sulfate radical anions (SO4˙) derived from the photolysis of persulfate ions by 308 nm excimer laser pulses. In neutral aqueous solutions (pH 7.0), the transient absorbance of neutral guanine radicals, G(-H)˙, is observed following the complete decay of SO4˙ radicals (~10 μs after the actinic laser flash). In both basket and hybrid conformations, the G(-H)˙ decay is biphasic with one component decaying with a lifetime of ~0.1 ms, and the other with a lifetime of 20–30 ms. The fast decay component (~0.1 ms) in G-quadruplexes is correlated with the formation of 8-oxoG lesions. We propose that in G-quadruplexes, G(-H)˙ radicals retain radical cation character by sharing the N1-proton with the O6-atom of G in the [G˙+: G] Hoogsteen base pair; this [G(-H)˙: H+G (Formula presented.) G˙+: G] leads to the hydration of G˙+ radical cation within the millisecond time domain, and is followed by the formation of the 8-oxoG lesions.

Original languageEnglish (US)
Pages (from-to)244-251
Number of pages8
JournalPhotochemistry and Photobiology
Volume95
Issue number1
DOIs
StatePublished - Jan 1 2019

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telomeres
G-Quadruplexes
Telomere
Electrons
Ions
Oxidation
oxidation
Conformations
Cations
baskets
Lasers
electrons
Photolysis
Guanine
Excimer lasers
Hydration
Excimer Lasers
lesions
Anions
Protons

ASJC Scopus subject areas

  • Biochemistry
  • Physical and Theoretical Chemistry

Cite this

Generation of 8-oxo-7,8-dihydroguanine in G-Quadruplexes Models of Human Telomere Sequences by One-electron Oxidation. / Merta, Tomasz J.; Geacintov, Nicholas; Shafirovich, Vladimir.

In: Photochemistry and Photobiology, Vol. 95, No. 1, 01.01.2019, p. 244-251.

Research output: Contribution to journalArticle

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