Ultraviolet resonant Raman spectroscopy of nucleic acid components

Abstract

The first resonant Raman excitation profile using UV as well as visible radiation is presented. Measurements of the intensity of the Raman spectrum of adenosine 5'-monophosphate as a function of the frequency of the incident laser light are presented in the range from 20 to 38 kK (1000 cm-1). The scattering intensity per molecule increases by about 10(5) as the laser is tuned from low to high frequencies. The Raman excitation profile has been calculated by using a simple form of the vibronic theory of Raman scattering. The theoretical curves are found to adequately fit the data using only the frequencies of the excited electronic states of AMP and their corresponding vibronic linewidths as adjustable parameters. The Raman bands at 1484 cm-1 and 1583 cm-1 appear to obtain virtually all of their intensity from a weak electronic transition at 276 nm. The set of Raman bands in the range 1300 cm-1-1400 cm-1 appear to derive at least part of their intensity from an electronic band whose 0-0 transition is in the 269-259 nm region although the possibility of some intensity arising from the vibronic mixing between these two electronic states cannot as yet be ruled out.