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Multiple Electronic and Structural Factors Control Cyclobutane Pyrimidine Dimer and 6-4 Thymine-Thymine Photodimerization in a DNA Duplex (20 visite)
Chemistry (ISSN: 1521-3765electronic, 0947-6539linking), 2017 Oct 26; 23(60): 15177-15188.
Tipo di articolo: Journal Article
Impact factor: 5.476
Impact factor a 5 anni: 5.477
Parole chiave: 64-Pp, Dft Calculations, Photodimerization, Thymine
Url: Non disponibile.
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 T(3) and a 5'-T-->3'-T charge transfer for CPD and oxetane formation, respectively, thus calling for specific electronic constraints.
*** IBB - CNR ***
Dipartimento di Chimica Industriale "T. Montanari", Universita di Bologna, Viale Risorgimento 4, 40136, Bologna, Italy., Istituto di Biostrutture e Bioimmagini, CNR, Via Mezzocannone 16, 80134, Napoli, Italy., TU Wien, Zentraler Informatikdienst, Wiedner Hauptstrasse 8-10, 1040, Wien, Austria., Department of Physics, Michigan Technological University, 1400 Townsend Drive, Houghton, MI, 49331-1295, USA., LIDYL, CEA, CNRS, Universite Paris, Saclay, 91191, Gif-sur-Yvette, France.,
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