Time-resolved study of thymine dimer formation.
The formation of thymine dimers in the single-stranded oligonucleotide, (dT)20, is studied at room temperature by laser flash photolysis using 266 nm excitation. It is shown that the (6-4) adduct is formed within 4 ms via a reactive intermediate. The formation of cyclobutane dimers is faster than 200 ns. The overall quantum yield for the (6-4) formation is (3.7 +/- 0.3) x 10-3, and that of the cyclobutane dimers is (2.8 +/- 0.2) x 10-2. No triplet absorption is detected, showing that either the intersystem crossing yield decreases by 1 order of magnitude upon oligomerization (<1.4 x 10-3) or the triplet state reacts with unit efficiency in less than 200 ns to yield cyclobutane dimers.
Marguet
Sylvie
S
Laboratoire Francis Perrin, CEA/DSM/DRECAM/SPAM-CNRS, URA 2453, CEA Saclay, 91191 Gif-sur-Yvette, France.
Markovitsi
Dimitra
D
D010782:Photolysis; D011071:Poly T / Q000737:chemistry / Q000528:radiation effects; D011740:Pyrimidine Dimers / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects*; D013938:Thymidine Monophosphate / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects*
D011740:Pyrimidine Dimers; D011071:Poly T; D013938:Thymidine Monophosphate