On the Deactivation Mechanisms of Adenine鈥揟hymine Base Pair

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• 作者：Jo茫o Paulo Gobbo ; Vicenta Saur铆 ; Daniel Roca-Sanju谩n ; Luis Serrano-Andr茅s ; Manuela Merch谩n ; Antonio Carlos Borin
• 刊名：The Journal of Physical Chemistry B
• 出版年：2012
• 出版时间：April 5, 2012
• 年：2012
• 卷：116
• 期：13
• 页码：4089-4097
• 全文大小：422K
• 年卷期：v.116,no.13(April 5, 2012)
• ISSN：1520-5207

文摘

In this contribution, the multiconfigurational second-order perturbation theory method based on a complete active space reference wave function (CASSCF/CASPT2) is applied to study all possible single and double proton/hydrogen transfers between the nucleobases in the adenine鈥搕hymine (AT) base pair, analyzing the role of excited states with different nature [localized (LE) and charge transfer (CT)], and considering concerted as well as step-wise mechanisms. According to the findings, once the lowest excited states, localized in adenine, are populated during UV irradiation of the Watson鈥揅rick base pair, the proton transfer in the N鈥揙 bridge does not require high energy in order to populate a CT state. The latter state will immediately relax toward a crossing with the ground state, which will funnel the system to either the canonical structure or the imino鈥揺nol tautomer. The base pair is also capable of repairing itself easily since the imino鈥揺nol species is unstable to thermal conversion.