Mobility-concentration effects for RNA in agar gel electrophoresis

The dependence of the mobility of RNA species on their concentration in agar gel electrophoresis is explained in terms of adsorption on the gel matrix. The number of interaction sites on RNA molecules depends on the origin of the RNA and on the extent of deproteinization. The ratio of sites on the RNA of the large and small ribosomal subunits is equal to the ratio of their molecular weights for both rat liver and E. coli . The results suggest that the interactions with the gel are due to some impurity, most probably protein.