Iodination of nucleic acids in organic solvents with iodine monochloride.

Iodine monochloride, labeled with 1z51, iodinated ribonucleic acid and deoxyribonucleic acid dissolved as hexadecyltrimethylammonium salts in anhydrous dimethylformamide or N-ethyl acetamide. In the case of RNA (polyuridylate, polycytidylate, and soluble RNA) 5-iodouridine S/-phosphate, 8-iodoguanosine 5’-phosphate, and 5-iodocytidine 5’-phosphate are found. After 24 hours of reaction, 32% of UMP, 8% of GMP, and 9% of CMP residues in soluble RNA were found to be iodinated. In the case of DNA, after 24 hours of reaction, 8-iodo-dGMP and 5-iodo-dCMP represent 1.4 and 14%, respectively, of the parent nucleotides present. The use of ion exchange column chromatography and ion exchange paper in the analysis of the iodinated nucleotides present in enzymatic digests of the nucleic acids is described. These techniques provide a means of introducing radioactivity into preformed polynucleotides and of studying the influence of iodinated bases on the biological activity of nucleic acids.