VIBRATIONAL ANALYSIS AND MOLECULAR-FORCE FIELD OF HYPOXANTHINE AS DETERMINED FROM ULTRAVIOLET RESONANCE RAMAN-SPECTRA OF NATIVE AND DEUTERATED SPECIES

Ultraviolet resonance Raman scattering spectra from aqueous solutions of hypoxanthine and its deuterated species (C8-deuterated, N-deuterate d and C8-, N-deuterated derivatives) have been collected and reported in the spectral region between 400 and 1800 cm(-1). The laser excitati on wavelengths at 281 nm and 257 nm correspond to preresonance and pur e resonance conditions, respectively, with the purine strongly allowed pi-->pi electronic transition: thus the observed experimental Raman features mainly correspond to inplane vibrational modes. The latter we re then assigned according to the Wilson GF method by using an empiric al harmonic valence force field. Normal mode calculations are based on a non-redundant set of internal coordinates. The calculated vibration al mode wavenumbers and their isotopic shifts upon selective deuterati ons are in good agreement with the experimental data. The present norm al mode analysis rests on the transferability of the guanine and adeni ne force constants proposed in recent works based on resonance Raman s pectroscopy and neutron inelastic scattering data from these major pur ine bases.