Balanikas E, Martinez-Fernandez L, Baldacchino G, Markovitsi D. Electron Holes in G-Quadruplexes: The Role of Adenine Ending Groups.
Int J Mol Sci 2021;
22:ijms222413436. [PMID:
34948235 PMCID:
PMC8704496 DOI:
10.3390/ijms222413436]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2021] [Revised: 11/30/2021] [Accepted: 12/01/2021] [Indexed: 11/16/2022] Open
Abstract
The study deals with four-stranded DNA structures (G-Quadruplexes), known to undergo ionization upon direct absorption of low-energy UV photons. Combining quantum chemistry calculations and time-resolved absorption spectroscopy with 266 nm excitation, it focuses on the electron holes generated in tetramolecular systems with adenine groups at the ends. Our computations show that the electron hole is placed in a single guanine site, whose location depends on the position of the adenines at the 3' or 5' ends. This position also affects significantly the electronic absorption spectrum of (G+)● radical cations. Their decay is highly anisotropic, composed of a fast process (<2 µs), followed by a slower one occurring in ~20 µs. On the one hand, they undergo deprotonation to (G-H2)● radicals and, on the other, they give rise to a reaction product absorbing in the 300-500 nm spectral domain.
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