Nucleotide clusters in deoxyribonucleic acids. I. Isolation of purine oligonucleotides

Abstract

The distribution of uninterrupted purine sequences in DNA has been studied by degradation of DNA with hydrazine and KOH, followed by DEAE-cellulose chromatography with a salt gradient. Conditions of hydrolysis previously reported have not yielded reproducible results. Reasons for this lack of reproducibility have been found to include excessively severe conditions of hydrazinolysis and the failure of alkaline hydrolysis to produce discrete oligonucleotides of a single type: Pu_np_n+1. There is a steady release of inorganic phosphorus until stable oligonucleotides of general formula Pu_np_n−1 are produced. The modified procedure described here has given reproducible results in our laboratory. An explanation of the mechanism of degradation of DNA by hydrazine and KOH is presented.