Studies on the preferential specificity of pancreatic ribonuclease as deduced from partial digests.

A two-dimensional “mapping” procedure (1) with paper electrophoresis and paper chromatography permits the separation and identification of the mono-, di-, tri-, and tetranucleotides obtained by digestion of tobacco mosaic virus ribonucleic acid with pancreatic ribonuclease (2). This procedure has also been used for the analysis of micrococcal nuclease digests of deoxyribonucleic acid (3) by the quantitative comparison of the major compounds found in incomplete as well as complete digests. Studies of this type afford a closer analysis of the hydrolytic activity of the nuclease than is possible if only the products of exhaustive digestion are examined. This report describes the investigation of partial pancreatic ribonuclease digests of ribonucleic acid from tobacco mosaic virus and from yeast. The results indicate that certain ribonuclease-sensitive bonds are cleaved much earlier in the course of digestion than others.