Terminal-sequence Studies of High-molecular-weight Ribonucleic. the Reaction of Periodate-oxidized Ribonucleosides , 5'-ribonucleotides and Ribonucleic Acid with Isoniazid.

1. The reaction products of isoniazid with periodate-oxidized ribonucleosides and 5'-ribonucleotides have been characterized as the monohydrazones. 2. The stability, chromatographic and electrophoretic properties of the hydrazones are described. 3. (3)H-labelled isoniazid was shown to react with the 5'-linked terminal adenosine and cytidine groups of periodate-oxidized Escherichia coli transfer RNA. One mole of isoniazid reacts with 27x10(3)g. of the transfer RNA. 4. One mole of (3)H-labelled isoniazid reacts with approx. 10(6)g. of rabbit-reticulocyte ribosomal RNA. After fractionation of the RNA into its two components and treating the fractionated material with pancreatic ribonuclease and ribonuclease T(1) evidence is presented for the existence of two 5'-linked terminal sequences in the 30s fraction and only one sequence in the 17s fraction. 5. The application of this method to determining terminal sequences of high-molecular-weight RNA is discussed.