Gas Phase Structure and Proton Transfer reaction of protonated (Cytosine-Guanine)H+ pair

RAFAEL JARA TORO; PHILIPPE MAITRE,; GUSTAVO A. PINO; JUAN ARANGUREN ; FRANCIS BERTHIAS; DEBORA SCUDERI; ANDRÉS CRUZ ORTÍZ; MAXIMILIANO ROSSA; ANNE ZEHNACKER

Cartagena

Encuentro; 10th International Meeting on Photodynamics and Related Aspects; 2018

Universidad Nacional de Colombia

One decade after Watson and Crick (WC) discovered the double-helix structure ofDNA,1 Hoogsteen (Hoo)2 reported a crystal structure in which the base pair had a different structure 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.3The 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 ionization4,5 or protonation of the base pair.4 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. For this reason, 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). In this presentation we will discuss the most important features on this finding as well as new advances on the systems related to the Collision and UV induced PT reaction in the WC isomer of the protonated CGH+, which is supported by DFT calculations.