Resonance Raman spectra of mononucleotides obtained with 266 and 213 nm ultraviolet radiation

Resonance Raman spectra of the nucleoside 5′‐monophosphates UMP, CMP, AMP, and GMP have been obtained with 266‐ and 213‐nm radiation, the fourth and fifth harmonics of a Nd:YAG laser. The 266‐nm radiation is resonant with the states giving rise to the first absorption band of the bases. The resulting spectra are in agreement with those reported previously using similar wavelength excitation but are generally of better quality. The 213‐nm radiation is resonant with those states giving rise to the second strong absorption band of the bases. The spectra obtained with this wavelength show several new features relative to the 266‐nm spectra, including strong enhancement of modes of the pyrimidines with a character similar to the e_2g ν₈ mode of benzene, relative enhancement of ring modes at 1580 and 729 cm⁻¹ in AMP, and strong enhancement of the 1670‐cm⁻¹ C = O mode of GMP. These enhancements are discussed in terms of previously reported preresonance behavior and predicted intensities based on CNDO bond‐order changes and normal‐mode calculations. The results of a preliminary study of the effect of the interaction of GMP with cis‐dichlorodiammineplatinum(II) on the 213‐nm resonance Raman spectrum is also discussed.