Sedimentation Constant–Molecular Weight Relation of Ribosomes

Abstract

ROUGHLY speaking, RNA of high molecular weight could be regarded as a polymer composed of nearly the same units as in the synthetic high polymer, if the minor differences in the structure of its base components are assumed to be negligible and hence the relation such as [η] = KM^α would be expected between its intrinsic viscosity [η] and its molecular weight, M, which has been well known for the synthetic high polymers since the pioneer works of Staudinger. Indeed, Kurland¹ proved it on the ribosomal RNA, reporting that the value of α is nearly 0.5. Summarizing the data reported hitherto, Iso² also pointed out the following relation: is applicable to the RNA of the high molecular weight, where S₀ is the sedimentation constant in Svedberg units and M the molecular weight. The value of the exponent in these formations is very close to those calculated theoretically on the model of spherical molecules of matted chains without free drain, a fact which provides us with an indirect support for the view of Hall and Doty³ that RNA molecules could be regarded as an ellipsoid of revolution hydrodynamically.