Characterization of the major compounds found in ribonuclease T-1 digests of ribonucleic acid. 3. Penta- and higher oligonucleotides.

The mono-, di-, tri-, and tetranucleotides resulting from complete ribonuclease T1 (1) digests of ribonucleic acid have been described in preceding papers (2, 3). More recently, buffers containing 7 M urea (4) were shown to facilitate greatly the fractionation of oligonucleotides according to chain length at neutral pH (5). Rechromatography in urea-containing buffers at pH 2.7 was found to resolve RNase T1-derived tetraand pentanucleotides according to the variation in net charge brought about by base composition (6). Thus, a fractionation of the tetraand pentamers, each terminating in guanosine 3’-phosphate, was achieved according to adenosine 3’-phosphate + cytidine 3’phosphate against uridine 3’.phosphate content. The present paper describes the separation of higher oligonucleotides of equal chain length from RNase T1 digests of high molecular weight MS2 and yeast RNA. Oligomers up to the decamer (n = 10) were fractionated by rechromatography in 7 til urea at pH 2.7 and 4.4. Applications of these procedures are discussed.