A spectroscopic study of the reaction of formaldehyde with deoxyribonucleic and ribonucleic acids

Abstract

1. 1. The formaldehyde reaction of Fraenkel-Conrat has been used as a measure of the degree of denaturation of calf thymus deoxyribonucleic acid subjected to heat or pH change. Under the proper conditions the formaldehyde reaction seems to be at least as sensitive and may be more sensitive than viscosity measurements for detecting a low degree of denaturation of deoxyribonucleic acid. 2. 2. Using the reaction with formaldehyde as a criterion for denaturation of deoxyribonucleic acid, it has been found that no very sharp transition temperature occurs for the conversion of native to denatured deoxyribonucleic acid unless the time of heating is kept short. Deoxyribonucleic acid will denature rather completely at 70°, by the above criterion, if heating is sufficiently prolonged. 3. 3. Using the criterion of reaction with formaldehyde, a reversible and an irreversible type of denaturation of deoxyribonucleic acid can be distinguished. Reversal of the reversible denaturation can be accomplished by adjusting the pH to 8.5. 4. 4. The reaction with formaldehyde of heat-denatured calf-thymus deoxyribonucleic acid, reisolated by alcohol precipitation from i M sodium chloride solution, has been compared with the reaction of ribonucleic acid with formaldehyde. The two materials behave in a remarkably similar manner. 5. 5. The possibility of using the formaldehyde reaction to decide whether a reversibly denatured deoxyribonucleic acid can act as a primer in Bollum's system for deoxyribonucleic acid synthesis has been discussed.