Structural identification of uric acid and its monohydrates by IR-UV double resonance spectroscopy

We have employed IR-UV double resonance spectroscopy to identify the tautomeric and isomeric structures of uric acid and its monohydrated clusters which are produced by the techniques of laser-desorption and supersonic-jet cooling. The IR spectrum obtained for bare uric acid exhibits four distinct NH stretching transitions assignable to those of the most stable triketo form. We have also observed the two most stable monohydrated clusters, each with uric acid in the triketo form and water bonded to either the N3H or N9H site. It is demonstrated that the R2PI spectra of these monohydrates can be separated by using the IR-purified spectroscopic method.