Multiple Electronic and Structural Factors Control Cyclobutane Pyrimidine Dimer and 6–4 Thymine–Thymine Photodimerization in a DNA Duplex

The T–T photodimerization paths leading to the formation of cyclobutane pyrimidine dimer (CPD) and 6–4 pyrimidine pyrimidone (64‐PP), the two main DNA photolesions, have been resolved for a T–T step in a DNA duplex by two complementary state‐of‐the‐art quantum mechanical approaches: QM(CASPT2//CASSC...

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Bibliographic Details
Published in:Chemistry : a European journal 2017-10, Vol.23 (60), p.15177-15188
Main Authors: Conti, Irene, Martínez‐Fernández, Lara, Esposito, Luciana, Hofinger, Siegfried, Nenov, Artur, Garavelli, Marco, Improta, Roberto
Format: Article
Language:English
Subjects:
64-PP
Charge transfer
Chemical Physics
Chemistry
Cyclobutane
Deoxyribonucleic acid
DFT calculations
DNA
photodimerization
Physics
Quantum mechanics
Thymine
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Summary:The T–T photodimerization paths leading to the formation of cyclobutane pyrimidine dimer (CPD) and 6–4 pyrimidine pyrimidone (64‐PP), the two main DNA photolesions, have been resolved for a T–T step in a DNA duplex by two complementary state‐of‐the‐art quantum mechanical approaches: QM(CASPT2//CASSCF)/MM and TD‐DFT/PCM. Based on the analysis of several different representative structures, we define a new‐ensemble of cooperating geometrical and electronic factors (besides the distance between the reacting bonds) ruling T–T photodimerization in DNA. CPD is formed by a barrierless path on an exciton state delocalized over the two bases. Large interbase stacking and shift values, together with a small pseudorotation phase angle for T at the 3′‐end, favor this reaction. The oxetane intermediate, leading to a 64‐PP adduct, is formed on a singlet T→T charge‐transfer state and is favored by a large interbase angle and slide values. A small energy barrier (
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201703237