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

Abstract : 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 (<0.3 eV) is associated to this path, likely contributing to the smaller quantum yield observed for this process. Eventually, a clear directionality is always shown by the electronic excitation characterizing the singlet photoactive state driving the photodimerization process: an exciton that is more localized on T3 and a 5′-T→3′-T charge transfer for CPD and oxetane formation, respectively, thus calling for specific electronic constraints.
Type de document :
Article dans une revue
Chemistry - A European Journal, Wiley-VCH Verlag, 2017, 23 (60), pp.15177 - 15188. 〈10.1002/chem.201703237〉
Liste complète des métadonnées

https://hal-cea.archives-ouvertes.fr/cea-01668979
Contributeur : Caroline Lebe <>
Soumis le : mercredi 20 décembre 2017 - 14:25:29
Dernière modification le : jeudi 15 mars 2018 - 15:03:58

Identifiants

Citation

Irene Conti, Lara Martinez-Fernandez, Luciana Esposito, Siegfried Hofinger, Artur Nenov, et al.. Multiple Electronic and Structural Factors Control Cyclobutane Pyrimidine Dimer and 6-4 Thymine-Thymine Photodimerization in a DNA Duplex. Chemistry - A European Journal, Wiley-VCH Verlag, 2017, 23 (60), pp.15177 - 15188. 〈10.1002/chem.201703237〉. 〈cea-01668979〉

Partager

Métriques

Consultations de la notice

83