Photo-CIDNP study of the splitting of the dinucleotide cis, syn-thymine dimer with reduced flavin as a sensitizer: Evidence for a thymine radical anion intermediate

P. J.W. Pouwels, R. Kaptein

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Photochemically induced dynamic nuclear polarization (photo-CIDNP) studies were performed on the splitting of cis,syn 2′-deoxythymidylyl-(3′→5′)-2′-deoxythymidine cyclobutane dimer (cs-dTp dT), using reduced flavin as a sensitizer. This system serves as a model for the light-induced repair mechanism of thymine dimers in DNA by the enzyme photolyase. The CIDNP spectrum shows enhanced absorption of the two C6-H protons of the corresponding monomer dTpdT, which demonstrates that a thymine radical anion is involved in the splitting of the dimer. This is supported by a similar CIDNP spectrum that is obtained with the electron-donor Nα-acetyl tryptophan as a sensitizer. This result suggests that the light-induced splitting of thymine dimers in DNA by photolyase also proceeds via the thymine radical anion. The small difference in intensity of the two CIDNP signals belonging to the C6-H protons shows that the unpaired electron in the monomer radical has a slight preference for the thymine moiety at the 5′ terminus.

Original languageEnglish
Pages (from-to)107-113
Number of pages7
JournalApplied Magnetic Resonance
Issue number1
Publication statusPublished - 1 Aug 1994
Externally publishedYes

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