|S. Marguet, D. Markovitsi
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)x10-3 and that of the cyclobutane dimers (2.8 +/- 0.2)x10-2. No triplet absorption is detected showing that either the intersystem crossing yield decreases by one order of magnitude upon oligomerization (<1.4x10-3) or the triplet state reacts with unit efficiency in less than 200 ns to yield cyclobutane dimers.
Maj : 05/12/2008 (649)