Pairing of the nucleobases guanine and cytosine in the gas phase studied by IR–UV double-resonance spectroscopy and ab initio calculations
- 29 January 2002
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Physical Chemistry Chemical Physics
- Vol. 4 (5) , 732-739
- https://doi.org/10.1039/b107429f
Abstract
We present R2PI, IR–UV and UV–UV double resonance measurements of the guanine–cytosine (G–C) dimer formed in a supersonic jet. We show that there is only one isomer of G–C in the investigated wavelength range from 33200 to 34100 cm−1. We assigned the observed G–C isomer to a specific structure, based on comparisons of the IR spectra of the G and C monomers with the G–C dimer in the range of the OH and NH stretching vibrations and ab initio-calculated vibrational frequencies and dimer stabilities. The cluster exhibits an HNH⋯O/NH⋯N/CO⋯HNH bonding similar to the Watson–Crick G–C base pair bonding but with C as the enol tautomer. We did not observe any keto–keto or enol–enol G–C dimers in the investigated wavelength region.Keywords
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