0471961 - BFÚ 2017 RIV GB eng J - Článek v odborném periodiku
Szabla, Rafal - Gora, R.W. - Šponer, Jiří
Ultrafast excited-state dynamics of isocytosine.
Physical Chemistry Chemical Physics. Roč. 18, č. 30 (2016), s. 20208-20218. ISSN 1463-9076. E-ISSN 1463-9084
Grant CEP: GA ČR(CZ) GA14-12010S
Institucionální podpora: RVO:68081707
Klíčová slova: perturbation-theory * relaxation mechanisms
Kód oboru RIV: BO - Biofyzika
Impakt faktor: 4.123, rok: 2016 ; AIS: 1.124, rok: 2016
DOI: https://doi.org/10.1039/c6cp01391k

The alternative nucleobase isocytosine has long been considered as a plausible component of hypothetical primordial informational polymers. To examine this hypothesis we investigated the excited-state dynamics of the two most abundant forms of isocytosine in the gas phase (keto and enol). Our surface-hopping nonadiabatic molecular dynamics simulations employing the algebraic diagrammatic construction to the second order [ADC(2)] method for the electronic structure calculations suggest that both tautomers undergo efficient radiationless deactivation to the electronic ground state with time constants which amount to tau(keto) = 182 fs and tau(enol) = 533 fs. The dominant photorelaxation pathways correspond to ring-puckering (pi pi* surface) and C = O stretching/N-H tilting (n pi* surface) for the enol and keto forms respectively. Based on these findings, we infer that isocytosine is a relatively photostable compound in the gas phase and in these terms resembles biologically relevant nucleobases. The estimated S-1> T-1 intersystem crossing rate constant of 8.02 x 10(10) s(-1) suggests that triplet states might also play an important role in the overall excited-state dynamics of the keto tautomer. The reliability of ADC(2)-based surface-hopping molecular dynamics simulations was tested against multireference quantum-chemical calculations and the potential limitations of the employed ADC(2) approach are briefly discussed.
Trvalý link: http://hdl.handle.net/11104/0269322