The Structural Duality of Nucleobases in Guanine Quadruplexes Controls Their Low-Energy Photoionization

Evangelos Balanikas (1, 2) , Lara Martinez-Fernandez (3) , Roberto Improta (4) , Peter Podbevšek (5) , Gérard Baldacchino (1, 2) , Dimitra Markovitsi (1, 2)

1 DICO - Dynamique et Interactions en phase Condensée
2 LIDYL - Laboratoire Interactions, Dynamiques et Lasers (ex SPAM)
3 UAM - Universidad Autónoma de Madrid
4 CNR - Consiglio Nazionale delle Ricerche [Napoli]
5 KI - National Institute of Chemistry [Llubljana]

Guanine quadruplexes are four-stranded DNA/RNA structures composed of a guanine core (vertically stacked guanine tetrads) and peripheral groups (dangling ends and/or loops). Such a dual structural arrangement of the nucleobases favors their photoionization at energies significantly lower than the guanine ionization potential. This effect is important with respect to the oxidative DNA damage and for applications in the field of optoelectronics. Photoionization quantum yields, determined at 266 nm by nanosecond transient absorption spectroscopy, strongly depend on both the type and position of the peripheral nucleobases. The highest value (1.5 × 10−2 ) is found for the tetramolecular structure (AG4A)4 in which adenines are intermittently stacked on the adjacent guanine tetrads, as determined by nuclear magnetic resonance spectroscopy. Quantum chemistry calculations show that peripheral nucleobases interfere in a key step preceding electron ejection: charge separation, initiated by the population of charge transfer states during the relaxation of electronic excited states.

Domaines: Chimie théorique et/ou physique

Evangelos Balanikas, Lara Martinez-Fernandez, Roberto Improta, Peter Podbevšek, Gérard Baldacchino, et al.. The Structural Duality of Nucleobases in Guanine Quadruplexes Controls Their Low-Energy Photoionization. Journal of Physical Chemistry Letters, 2021, 12 (34), pp.8309-8313. ⟨10.1021/acs.jpclett.1c01846⟩. ⟨cea-03346313⟩