Raman spectra and analysis of polynucleotides containing adenosine residues

Abstract

Seven salts of adenosine 5′-monophosphoric acid were synthesized and studied by Raman spectroscopy. The barium salt structure is known to adopt the C(4′)-exo-anti nucleoside conformation, whereas adenosine 5′-monophosphoric acid has the C(2′)-endo-anti nucleoside structure. The structures of the other compounds reported in this work are, as yet, unknown. However, their Raman spectra indicate through their phosphoester stretching bands that they adopt either the C(3′)-endo-anti or the C(2′)-endo-anti nucleoside conformations. It is shown that the 1200–1400 and 600–850 cm^–1 regions provide some spectral features generated by the different nucleoside conformations, particularly C(2′)-endo-anti, C(3′)-endo-anti and C(4′)-exo-anti, as a result of vibrational coupling between the motions of ribofuranose and purine rings. These spectral features allow these different geometries to be characterized by this technique. A Raman spectroscopic analytical method is also described for the estimation of the percentages of adenosine residues in polynucleotides.