Preparative density gradient centrifugation of RNA and DNA in cesium sulfate-urea mixture

A new procedure is described for a large scale separation and purification of unfixed DNA and RNA from a mixture of partially extracted nucleic acids and lysates of subcellular fractions by centrifugation to equilibrium in cesium sulfate-urea mixture. Optimum conditions are described for the separation and quantative recovery of both RNA and DNA in a pure form. The procedure allows determination of peak buoyant densities of 4-5s RNA, 7-11s mRNA and total cytoplasmic RNA. The procedure also allows fractionation of small molecular weight classes of cytoplasmic RNAs from the 18s and 28s rRNAs.