Ribonucleic acid and protein content of eukaryotic ribosomes isolated from Artemia salina

Abstract

We are studying the ribosomes from the cryptobiotic embryos of Artemia salina. Here we report on the relation between the optical density at 260 nm of a ribosome solution and its RNA and protein content. Using the original Lowry method or a modified version, it has been found that 1 A 260 unit contains 42.4 ± 1.6 μg of protein, and, from the phosphorus content, that the same solution contains 41.6 ± 1.0 μg of RNA. Analytical isodensity equilibrium centrifugation gives a value of 1.570 ± 0.005 g/cm 3 for the buoyant density of these ribosomes in CsCl. This density can be related to a protein content of 51%, which is in accord with the chemical determinations. The relation between the optical density of ribosomes, RNA, and protein content and the optical density of rRNA of different systems, such as Escherichia coli, yeast, A. salina, and rat liver is discussed.