Theoretical study on the excited-state π-stacking versus intermolecular hydrogen-transfer processes in the guanine–cytosine/cytosine trimer

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• 作者：Antonio Francés-Monerris ; Javier Segarra-Martí…
• 关键词：Quantum chemistry ; Excited states ; CASSCF/CASPT2 ; DNA tautomerisation ; Cyclobutane cytosine dimer ; Hydrogen transfer ; UV light
• 刊名：Theoretical Chemistry Accounts: Theory, Computation, and Modeling (Theoretica Chimica Acta)
• 出版年：2016
• 出版时间：February 2016
• 年：2016
• 卷：135
• 期：2
• 全文大小：1,329 KB
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• 作者单位：Antonio Francés-Monerris (1)
  Javier Segarra-Martí (1) (2)
  Manuela Merchán (1)
  Daniel Roca-Sanjuán (1)
  
  1. Institut de Ciència Molecular, Universitat de València, P.O. Box 22085, 46071, Valencia, Spain
  2. Dipartimento di Chimica “G. Ciamician”, Via Selmi 2, 40126, Bologna, Italy
  
• 刊物类别：Chemistry and Materials Science
• 刊物主题：Chemistry
  Theoretical and Computational Chemistry
  Inorganic Chemistry
  Organic Chemistry
  Physical Chemistry
  
• 出版者：Springer Berlin / Heidelberg
• ISSN：1432-2234

文摘

Understanding the complex events that take place in nucleic acids upon UV light exposure constitutes a key step in the comprehension of life evolution, as well as in the determination of the mechanisms that can originate genetic mutations and lead to the development of diseases like skin cancer. Over the last decade, intra- and inter-strand processes that depend on the relative movements of the DNA strands have been proposed as photochemical pathways capable to deactivate the excess of energy provided by UV light. In order to elucidate the relative importance of both types of photochemical routes, high-level ab initio quantum chemical computations have been conducted on a model formed by the guanine–cytosine base pair and an additional π-stacked cytosine yielding a GC/C trimeric system. The effect of the π-stacking has been evaluated along the reaction coordinate of the stepwise double-hydrogen-transfer (SDHT) mechanism reported in a previous study (Sauri et al. in J Chem Theory Comput 9: 481–496, 2013). It becomes apparent from the present findings that the SDHT process is available at a wide range of cytosine–cytosine intermolecular distances. At a face-to-face orientation of the two cytosine molecules with an intermolecular distance of 3.4 Å, the highly effective π-stacking interaction favours the formation of the CC excimer of the canonical nucleobases. Nevertheless, no barriers are found for the inter-strand mechanism. At larger interacting distances (4.0 Å), both intra-strand photochemistry and inter-strand photochemistry have to be simultaneously considered, whereas at very short distances (2.8 Å) the SDHT process is significantly hindered. The present work confirms the availability of the intermolecular hydrogen transfer in a wide region of the distinct hypersurfaces explored. As compared to the canonical WC base pair, the tautomeric form has more favourable SDHT channels.