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Séminaire LCP-ISMO Gustavo Pino - vendredi 14 juin à 13h30


Séminaire LCP-ISMO Gustavo Pino - vendredi 14 juin à 13h30

Gustavo A. Pino, INFIQC (CONICET – UNC), Universidad Nacional de Córdoba, Argentina. International Associated Laboratory : LEMIR (CONICET – CNRS)

Vendredi 14 juin à 13h30 (salle Magat) :

Gas Phase Structure and Fragmentation of protonated (Cytosine-Guanine)H+ pair

Résumé
One decade after Watson and Crick (WC) discovered the double-helix structure of DNA[1], Hoogsteen (Hoo) [2] reported a crystal structure in which the base pair had a different motif from that reported by WC. The same year, 1963, Löwdin proposed that a proton transfer (PT) reaction within the WC pair could give rise to point mutations by formation of rare tautomers [3]. The activation energy barriers for these PT reactions are on the order of 58-67 kJ/mol [4], then at room temperature this process can only take place by tunneling. However, it has been suggested that these barriers are strongly reduced upon ionization [4,5] or protonation of the base pair [4].
Protonation of the nucleobases is known to induce the formation of proton mediated Hoogsteen (Hoo) pairs, which play an important role in many biological processes [6]. WC isomers are more stable than Hoo structures under physiological pH, but under slightly acidic conditions the Hoo pairs become most stable one [7].
In this context, it thus seems that detailed studies at the molecular level of protonated DNA base pairing structure and reactivity is of high importance. We have recently reported the gas phase characterization of the protonated Cytosine-Guanine (CGH+) either in the WC or Hoo isomeric structures using Tandem Mass-Spectrometry coupled to MS/MS, InfraRed Multiphoton Dissociation (IRMPD) spectroscopy and Differential Ion Mobility Spectrometry (DIMS) [8].
In this presentation we will discuss the most important features on this finding as well as new advances on this system, related to the Collision and UV induced dissociation of the WC isomer and Hoo isomers of the protonated CGH+, which is supported by DFT calculations.

References :
[1] Watson, J. D. ; Crick, F. H. Nature 1953, 171, 737–738.
[2] Hoogsteen, K.. Acta Crystallogr. 1963, 16, 907-916.
[3] Lowdin, P. O. Rev. Mod. Phys. 1963, 35, 724-732.
[4] Bertran, J. ; Blancafort, L. ; Noguera, M. ; Sodupe, M. Proton Transfer in DNA Base Pairs. In Computational Studies of RNA and DNA ; Sponer, J. ; Lankas, F., Eds. ; Springer : Netherlands, 2006.
[5] Nir, E. ; Kleinnermans, K. ; de Vries, M. S. Nature 2000, 408, 949-951.
[6] Arcella, A. ; Portella, G. ; Orozco, M. Structure of Nucleic Acids in the Gas Phase (Chap. 3, 55-76). In Nucleic acids in the gas phase ; Gabelica, V., Ed. ; Springer-Verlag : Berlin, 2014.
[7] Alvey, H. S. ; Gottardo, F. L. ; Nikolova, E. N. ; Al-Hashimi, H. M. Nat. Comm. 2014, 5, 4786:1-8.
[8] Cruz Ortiz, A. F. ; Rossa, M. ; Berthias, F. ; Berdakin, M. ; Maitre, P. ; Pino, G. A. J. Phys. Chem. Lett. 2017, 8, 5501-5506.

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