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On the photoproduction of DNA/RNA cyclobutane pyrimidine dimers
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Physical and Analytical Chemistry, Quantum Chemistry.
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2011 (English)In: Theoretical Chemistry accounts, ISSN 1432-881X, E-ISSN 1432-2234, Vol. 128, no 4-6, 705-711 p.Article in journal (Refereed) Published
Abstract [en]

The UV photoreactivity of different pyrimidine DNA/RNA nucleobases along the singlet manifold leading to the formation of cyclobutane pyrimidine dimers has been studied by using the CASPT2 level of theory. The initially irradiated singlet state promotes the formation of excimers between pairs of properly oriented nucleobases through the overlap between the pi structures of two stacked nucleobases. The system evolves then to the formation of cyclobutane pyrimidine dimers via a shearing-type conical intersection activating a [2 + 2] photocycloaddition mechanism. The relative location of stable excimer conformations or alternative decay channels with respect to the reactive degeneracy region explains the differences in the photoproduction efficiency observed in the experiments for different nucleobases sequences. A comparative analysis of the main structural parameters and energetic profiles in the singlet manifold is carried out for thymine, uracil, cytosine, and 5-methylcytosine homodimers. Thymine and uracil dimers display the most favorable paths, in contrast to cytosine. Methylation of the nucleobases seems to increase the probability for dimerization.

Place, publisher, year, edition, pages
2011. Vol. 128, no 4-6, 705-711 p.
Keyword [en]
CASPT2, Photochemisty, Conical Intersection, DNA/RNA, Cyclobutane Pyrimidine Dimers
National Category
Chemical Sciences
URN: urn:nbn:se:uu:diva-149564DOI: 10.1007/s00214-010-0854-zISI: 000287748900032OAI: oai:DiVA.org:uu-149564DiVA: diva2:405269
Available from: 2011-03-22 Created: 2011-03-21 Last updated: 2011-03-22Bibliographically approved

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