A simple and sensitive method is described for the assay of ribonucleotide reductase. The advantage of this system is improved separation of ribonucleotides and their corresponding deoxyribonucleotides by paper chromatography using a filter paper impregnated with 0.1 m boric acid. A ribonucleotide reductase system from Rhizobium meliloti could be easily assayed by carrying out this paper chromatography of the sample obtained from the enzymic reaction with 14 C-labeled substrate.
