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RESEARCH PRODUCT
Photoinduced Formation Mechanism of the Thymine−Thymine (6−4) Adduct
Daniel Roca-sanjuánAngelo GiussaniMarco GaravelliLuis Serrano-andrésManuela Merchánsubject
Models MolecularDouble bondUltraviolet RaysphotolesionDimerÀcids nucleicsQuantum yieldthymine−thymine dimer010402 general chemistryPhotochemistry01 natural sciencesAdductDNA Adductschemistry.chemical_compound0103 physical sciencesMaterials ChemistryPhysical and Theoretical Chemistrychemistry.chemical_classificationphotochemistry010304 chemical physicsChemistryDNA3. Good health0104 chemical sciencesSurfaces Coatings and FilmsThymineIntersystem crossingPyrimidine DimersExcited stateCASPT2//CASSCFQuantum TheoryGround stateFisicoquímicadescription
The photoinduced mechanism leading to the formation of the thymine-thymine (6-4) photolesion has been studied by using the CASPT2//CASSCF approach over a dinucleotide model in vacuo. Following light absorption, localization of the excitation on a single thymine leads to fast singlet-triplet crossing that populates the triplet (3)(nπ*) state of thymine. This state, displaying an elongated C(4)═O bond, triggers (6-4) dimer formation by reaction with the C(5)═C(6) double bond of the adjacent thymine, followed by a second intersystem crossing, which acts as a gate between the excited state of the reactant and the ground state of the photoproduct. The requirement of localized excitation on just one thymine, whose main decay channel (by radiationless repopulation of its ground state) is nonphotochemical, can rationalize the experimentally observed low quantum yield of formation for the thymine-thymine (6-4) adduct.
| year | journal | country | edition | language |
|---|---|---|---|---|
| 2013-01-01 |