The action ofγ-rays on sodium deoxyribo-nucleate in solution

Abstract

The effect of irradiation by gamma-rays from a cobalt-60 source, without exclusion of oxygen, on the molecular structure of herring sperm sodium deoxyribonucleate (DNA) has been studied with the following aims: (i) to obtain evidence on the existence of the double-helical DNA structure in aqueous solution by testing the application of recent theoretical treatments for the random fracture of single-chain macromolecules (Charlesby 1954); and (ii) to study the effects of dosages of gamma-rays lower than those which have been shown to disrupt the constituent nucleotides. Changes in viscosity, electrometric titration behavior, ultra-violet absorption, precipitability and other chemical properties have been investigated. The viscosity of solutions of DNA in 0.1 M-sodium chloride was decreased on irradiation by an amount which was independent of the dose rate and was determined by the ratio (R, in eV/atom of DNA phosphorus) of dosage in eV entering each ml of solution to concentration of DNA phosphorus. The reduced specific viscosity of irradiated DNA solutions was a linear function of concentration and obeyed the Huggins equation (Huggins 1942). The intrinsic viscosity [[eta]