Radiosensitivity of Hydrogen Bonds in Deoxyribonucleic Acid

Abstract

ALEXANDER et al.¹ have suggested that the ‘secondary’ structure of deoxyribonucleic acid (DNA) is disorganized after irradiation by breaking the hydrogen bonds which link the two molecules together into the twin helix. “In regions of the DNA molecule where this occurs, the double molecule is opened up and becomes more flexible.” The molecule can coil up then into a smaller volume in solution and the viscosity of this solution will decrease. A further decrease in the viscosity is observed when the molecule is degraded due to breaks in the polynucleotide chain. As the loss of the viscosity is a result of different radiation effects, it is of interest to study tho effect of the irradiation on the hydrogen bonds with other methods. The wrork of Sarkar and Dounce² provides a basis for such studies. According to these authors the formaldehyde reaction of Fraenkel-Conrat³ can be observed only when an appreciable disruption of the interstrand hydrogen bonds occurs. This formaldehyde reaction may be more sensitive than viscosity measurements for detecting a low degree of denaturation of DNA. While Sarkar and Dounce² studied the denaturation after heating, I compared their results with the denaturation by X-ray irradiation.