21 April 2022

Séminaire ICP Dimitra Markovitsi – jeudi 21 avril à 14h

An intriguing effect: low-energy photoionization of DNA

DNA photoionization in aqueous solutions was reported in the 1990s for excitation wavelengths <200 nm. Recently, it appeared that it may occur at wavelengths corresponding to energies significantly lower than the ionization potential of its components. Time-resolved absorption studies with 267 nm excitation, revealed that this process strongly depends on the secondary DNA structure, guanine quadruplexes exhibiting the highest propensity to undergo photo-induced electron ejection. This unexpected effect, with biological and technological implications, has been correlated with charge transfer states populated during the excited state relaxation. In addition, it allows the determination of the reaction dynamics of the generated electron holes (radical cations), also affected by the secondary structure.

Key references:

Balanikas, E.; Banyasz, A.; Douki, T.; Baldacchino, G.; Markovitsi, D. Guanine Radicals Induced in DNA by Low-Energy Photoionization. Acc. Chem. Res. 2020, 53, 1511;

Balanikas, E.; Banyasz, A.; Baldacchino, G.; Markovitsi, D. Deprotonation Dynamics of Guanine Radical Cations. Photochem. Photobiol. 2021;

Balanikas, E.; Martinez-Fernadez, L.; Improta, R.; Podbevsek, P.; Baldacchino, G.; Markovitsi, D. The Structural Duality of Nucleobases in Guanine Quadruplexes Controls Their Low-Energy Photoionization. J. Phys. Chem. Lett. 2021, 12, 8309;

Balanikas, E.; Markovitsi, D.: DNA photoionization: from high to low energies. In DNA Photodamage: From Light Absorption to Cellular Responses and Skin Cancer; Improta, R., Douki, T., Eds.; Comprehensive Series in Photochemical and Photobiological Science 21; RSC: Cambridge, 2021; pp 37-54.

21 April 2022, 14h0015h00
Salle Magat, bâtiment 349, ICP