RAMAN-SPECTRA AND ANALYSIS OF POLYNUCLEOTIDES CONTAINING ADENOSINE RESIDUES

Seven salts of adenosine 5'-monophosphoric acid were synthesized and s tudied by Raman spectroscopy. The barium salt structure is known to ad opt the C(4')-exo-anti nucleoside conformation, whereas adenosine 5'-m onophosphoric acid has the C(2')-endo-anti nucleoside structure. The s tructures of the other compounds reported in this work are, as yet, un known. However, their Raman spectra indicate through their phosphoeste r stretching bands that they adopt either the C(3')-endo-anti or the C (2')-endo-anti nucleoside conformations. It is shown that the 1200-140 0 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 coupl ing between the motions of ribofuranose and purine rings. These spectr al features allow these different geometries to be characterized by th is technique. A Raman spectroscopic analytical method is also describe d for the estimation of the percentages of adenosine residues in polyn ucleotides.