A Proposed Interpretation of Infra-red Spectral Changes occurring upon the Interaction of Polynucleotides

Abstract

IT has been found that the sodium salts of polyadenylic and polyuridylic acids interact^1–4 with formation of a two-stranded helix¹ with a structure very similar to deoxyribonucleic acid. More recently it was observed that the infra-red spectrum⁵ of the mixture of these two acids showed the following marked changes from the summation of the curves of the components : a 39 per cent reduction in intensity of the 1,627 cm.⁻¹ band and a 7 cm.⁻¹ shift to higher frequency ; a decrease in peak height (because of strong overlap the band was not integrated) and an 11 cm.⁻¹ shift to higher frequency of the 1,661 cm.⁻¹ band. The interaction of the sodium salts of polycytidylic and polyinosinic acids⁶ has now been observed in the infra-red⁷ with the following result : a marked decrease in intensity of the 1,651 cm.⁻¹ peak of the sodium salt of polycytidylic acid (the intensities have not yet been put on a quantitative basis) and a 19 cm.⁻¹ shift to higher frequency of the 1,678 cm.⁻¹ peak of the sodium salt of polyinosinic acid.