The nature of polydisperse ribonucleic acid in plants

The aggregation of ribosomal RNA species during chromatography on methylated albumin on kieselguhr was decreased from 50 to 15% by the lower salt concentrations made possible by the use of higher pH values. The polydisperse RNA was resolved into two fractions. About 50% was eluted with the rRNA whereas the remainder was bound to the column, and was recovered only by solubilization of the methylated albumin. Both fractions of polydisperse RNA were similar in size range, but the bound fraction was considerably richer in AMP. No D-RNA (DNA-like RNA) peak was resolved under these conditions of column fractionation. However, the properties of the bound RNA were consistent with it containing both D-RNA and TB-RNA (tenaciously bound RNA). The relationship between these two fractions of AMP-rich RNA was considered. The bound RNA and ribosomal RNA responded differently to various treatments. The salt concentration required to elute ribosomal RNA was halved by increasing the pH of the fractionation, but the amount of bound RNA was in fact increased. Denaturation by hot urea decreased the binding of ribosomal RNA to the methylated albumin, but did not facilitate elution of bound RNA. The high affinity between the AMP-rich polydisperse RNA and the methylated albumin does not therefore appear to arise for the secondary structure conferred by the high AMP content.