Polymerization of ribomononucleotides by γ-radiation

1. 1. After γ-irradiation (0.9–18.0·10 4 R) of ribomononucleotides in aqueous solution a decrease in absorbancy at 260 mμ of at least two different components is observed. This decrease is an exponential function of the dose. 2. 2. Alkaline and enzymic hydrolysis with RNAase or phosphodiesterase of the irradiated samples produces an hyperchromic effect. 3. 3. Paper chromatography shows that the irradiated product has a lower R F than the mononucleotides. After alkaline or phosphodiesterase hydrolysis the R F approaches again that of the controls. 4. 4. The irradiated samples were chromatographed on a DEAE-cellulose column. Stronger anions (polymers) with a nucleic acid-like absorption spectrum were separated from the original mononucleotides by elution with increasing concentrations of NH 4 HCO 3 . 5. 5. The polymers formed by radiation decrease or disappear if the samples are incubated with alkali or enzymes before adsorption on the column. 6. 6. There is a correlation between the size of the polymers formed and the dose of γ-rays used. 7. 7. Irradiated samples excited at 310 mμ have a fluorescence at 400 mμ, not shown by the mononucleotides, directly related to the dose and decreasing after alkaline hydrolysis. 8. 8. Irradiated deoxyribomononucleotides (14.4·10 4 R) show a decrease in absorbancy at 260 mμ, which is partially reversed after incubation with deoxyribonuclease. 9. 9. The polymerization through phosphodiester bonds after γ-radiation of ribomononucleotides is discussed.