Raman studies of nucleic acids IV: Vibrational spectra and associative interactions of aqueous inosine derivatives

Abstract

Laser-excited Raman spectra of H 2O and 2H 2O solutions of inosine, inosine-5′-monophosphate and I-methylinosine are reported. The spectra are discussed in terms of the changes in molecular structure produced by changes in pH and p 2H. The temperature dependence of Raman scattering intensities from aqueous inosine and inosine-5′-monophosphate are also reported. Raman hypochromism occurs in several lines in the spectra and is attributed to stacking of the hypoxanthine rings at low temperature. The association of the nucleotide is accompanied by enhanced Raman scattering near 820 cm −1, similar to that observed previously for ordered polynucleotide structures and RNA. Effects of solute concentration and Mg 2+ concentration on spectra of the nucleotide are also discussed. The Raman data suggest that the nucleotide bases are stacked singly and that the phosphate substituents are largely unaffected in structure and environment by the base stacking.