Fingerprints of Both Watson–Crick and Hoogsteen Isomers of the Isolated (Cytosine-Guanine)H + Pair

BERTHIAS, FRANCIS; PINO, GUSTAVO A.; ROSSA, MAXIMILIANO; MAITRE, PHILIPPE; CRUZ-ORTIZ, ANDRÉS F.; BERDAKIN, MATÍAS

The Journal of Physical Chemistry Letters

American Chemical Society

Año: 2017 p. 5501 - 5506

1948-7185

Gas phase protonated guanine-cytosine (CGH+) pair was generated using an electrospray ionization source from solutions at two different pH (5.8 and 3.2). Consistent evidence from MS/MS fragmentation patterns and differential ion mobility spectra (DIMS) point toward the presence of two isomers of the CGH+ pair, whose relative populations depend strongly on the pH of the solution. Gas phase infrared multiphoton dissociation (IRMPD) spectroscopy in the 900−1900 cm−1 spectral range further confirms that theWatson−Crick isomer is preferentially produced (91%) at pH = 5.8, while the Hoogsteen isomer predominates (66%) at pH = 3.2). These fingerprint signatures are expected to be useful for the development of new analytical methodologies and to trigger isomer selective photochemical studies of protonated DNA base pairs.