Changes in the infrared spectra of solutions of deoxypentose nucleic acid in relation to its structure

Abstract

High molecular weight deoxypentose nucleic acid (DNA) in aqueous solution has a characteristics infrared spectrum which may be changed by physica, chemical, or enzymic treatment. The region of the spectrum in which the most important changes occur is that associated with the purine and pyrimidine components. In particular, two strong absorption bands at 1680 and 1645 cm −1 disappear upon (a) raising the pH over 11, or () heating the solution for a few minutes at 100° C, or (c) upon short treatment with desoxyribonuclease. Concomitant with the disappearance of the absorption bands at 1680 and 1645 cm −1 is the appearance of two new bands at 1660 and 1625 cm − We have not been able to reverse changes in the infrared absorption spectra of DNA in solution once they have occurred. The observed infrared spectral changes of DNA in solution, with the treatments described above, lie in the region where purine-pyrimidine absorption occurs and are indicative of the important role these bases must play in the molecular configuration of DNA. The nature and extent of the spectral shifts are such as to lead us to postulate that such treatments irreversibly alter the specific double stranded helical configuration of the original high molecular weight DNA.