Preparation of 35S-labeled ribonucleic acid and deoxyribonucleic acid and their use for the assay of nucleolytic enzymes (nucleosides and nucleotides. XXXIX.

Abstract

Radioactive sulfur was introduced into ribonucleic acid (RNA) and deoxyribonucleic acid (DNA) molecules by chemical means. The thio group in 4-thiouracil residues, which were introduced into RNA and DNA by sulfhydrolysis, was exchanged with radioactive Na2S via a 4-thiocyanatouracil intermediate. Specific activity of the 35S-labeled RNA and DNA was around 105 cpm/ODU260. The labeled RNA and DNA were successfully applied as substrates for the assay of nucleolytic enzymes or ribonuclease inhibitor. The sensitivity of the assay was 100 times better than that of the current method using non-labeled nucleic acids as the substrate.