Photodynamics of alternative DNA base isoguanine

0509623 - BFÚ 2020 RIV GB eng J - Journal Article
Gate, G. - Szabla, Rafal - Haggmark, M. R. - Šponer, Jiří - Sobolewski, A. L. - de Vries, M. S.
Photodynamics of alternative DNA base isoguanine.
Physical Chemistry Chemical Physics. Roč. 21, č. 25 (2019), s. 13474-13485. ISSN 1463-9076. E-ISSN 1463-9084
Institutional support: RVO:68081707
Keywords : excited-state dynamics * polarization propagator * perturbation-theory * pyrimidine-bases
OECD category: Physical chemistry
Impact factor: 3.430, year: 2019
Method of publishing: Open access
https://pubs.rsc.org/en/content/articlepdf/2019/cp/c9cp01622h

Isoguanine is an alternative nucleobase that has been proposed as a component of expanded genetic codes. It has also been considered as a molecule with potential relevance to primordial informational polymers. Here, we scrutinize the photodynamics of isoguanine, because photostability has been proposed as a critical criterion for the prebiotic selection of biomolecular building blocks on an early Earth. We discuss resonance-enhanced multiphoton ionization, IR-UV double resonance spectroscopy and pump-probe measurements performed for this molecule to track the excited-state behaviour of its different tautomeric forms in the gas phase. These experiments, when confronted with highly accurate quantum chemical calculations and nonadiabatic dynamics simulations provide a complete mechanistic picture of the tautomer-specific photodynamics of isoguanine. Our results indicate that UV-excited enol tautomers of isoguanine are relatively short lived and therefore photostable. In contrast, the biologically more relevant keto forms are trapped in dark n pi* states which are sufficiently long lived to participate in destructive photochemistry. The resulting lower photostability compared to canonical nucleobases may have been one of the reasons why isoguanine was not incorporated into DNA and RNA.
Permanent Link: http://hdl.handle.net/11104/0300311