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Spectroscopy: An International Journal
Volume 27 (2012), Article ID 168286, 20 pages

Guanine: A Combined Study Using Vibrational Spectroscopy and Theoretical Methods

1Research Unit “Molecular Physical-Chemistry”, Department of Chemistry, Faculty of Science and Technology, University of Coimbra, 3004-535 Coimbra, Portugal
2Department of Life Sciences, University of Coimbra, 3001-401 Coimbra, Portugal
3ISIS Facility, The Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, UK

Copyright © 2012 R. Pedro Lopes et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The present paper reports a conformational study of solid-state anhydrous guanine, using vibrational spectroscopy techniques—infrared, Raman, and inelastic neutron scattering—coupled to quantum mechanical methods at the DFT level, both for the isolated molecule and the condensed state. In both cases, the 7H-keto-amino tautomer was found to be the prevalent form, contrary to aqueous solutions and hydrated polycrystalline guanine, where the 9H-keto-amino tautomer is the most favoured species. This paper is a significant contribution for the existing spectroscopic characterization of this purine base, by unambiguously assigning its vibrational spectra.