Electron donor-acceptor interactions with flanking purines influence the efficiency of thymine photodimerization

Zhengzheng Pan, Mahesh Hariharan, Joshua D. Arkin, Almaz S. Jalilov, Martin McCullagh, George C Schatz*, Frederick D Lewis

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

44 Scopus citations


Quantum yields for thymine photodimerization (φTT) have been determined for a series of short DNA single-strand and base-paired hairpin structures possessing a single thymine-thymine step with flanking purines. Values of φTT are strongly dependent upon the oxidation potential of the flanking purine, decreasing in the order: inosine > adenine > guanine > deazaguanine. The dependence of φTT on the ionization potential of the flanking purine is more pronounced when the purine of lower oxidation potential is located at the 5′- versus 3′-position in either a single strand or a hairpin. Molecular dynamics simulations for hairpin structures indicate that the TT step is π-stacked with both the 5′ and 3′ purine, but that there is little π-stacking with either purine in single-strand structures. The observation of moderately intense long-wavelength UV absorption features for hairpins having 5′-Z or G flanking purines suggests that excitation of ground state donor-acceptor complexes may account for more extensive quenching of dimerization by 5′- versus 3′-purines. The "purine effect" on φTT is attributed to a combination of ground state conformation, ground state electron donor-acceptor interactions, and excited state exciplex formation.

Original languageEnglish (US)
Pages (from-to)20793-20798
Number of pages6
JournalJournal of the American Chemical Society
Issue number51
StatePublished - Dec 28 2011

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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