Article Dans Une Revue Journal of Physical Chemistry A Année : 2002

Tautomerism of the DNA Base Guanine and Its Methylated Derivatives as Studied by Gas-Phase Infrared and Ultraviolet Spectroscopy

Résumé

The present IR-UV depletion spectroscopic study extends the recent data of literature by providing evidence for the existence of a fourth form of guanine in the gas phase. The comparison of the UV and IR signatures of the four forms together with those of the 7- and 9-methylated derivatives allows us to build up a new assignment in terms of enol/keto and 7/9NH tautomerisms. From this complete picture, it turns out that the UV spectroscopy of free guanine is mainly controlled by the 7/9NH tautomerism: both 7NH tautomers observed are red-shifted compared to the 9NH ones, with the following origin transition order, from red to blue: 7NH enol (32864 ± 5 cm-1), 7NH keto (+405 cm-1), 9NH keto (+1046 cm-1), and 9NH enol (+1891 cm-1); 7-, 9- or 1-methylations are found to cause only moderate red shifts (less than 400 cm-1). The opposite trend is observed for the IR spectroscopy, which appears to be essentially controlled by the enol/keto tautomerism. This study exemplifies the need for cross-checked experimental approaches, namely the IR/UV depletion spectroscopy or the study of relevant methylated species, to reach a global and consistent assignment, even in rather simple biological systems such as purine bases.

Dates et versions

hal-00144500 , version 1 (03-05-2007)

Identifiants

Citer

M. Mons, I. Dimicoli, F. Piuzzi, B. Tardivel, M. Elhanine. Tautomerism of the DNA Base Guanine and Its Methylated Derivatives as Studied by Gas-Phase Infrared and Ultraviolet Spectroscopy. Journal of Physical Chemistry A, 2002, 106 (20), pp.5088-5094. ⟨10.1021/jp0139742⟩. ⟨hal-00144500⟩
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