Electron Microscope Observations on the Structure of Ribosomes from Calf Liver.

Ribosomes from liver are known to exist in a number of different stable forms, depending foremost on the concentration of free magnesium ions, and characterized by sedimentation coefficients of 120s, 80s, 60s and 40s. These different forms have been investigated by electron microscopy, using phosphotungstic acid staining. It was found that the 120s particles consisted of two 80s particles jointed together as a dimer. The 80s particles could be seen to contain two subunits of unequal size with a well-marked cleft between them. Electron microscope observations, after EDTA and urea treatment on the preparations of calf liver ribosomes, suggest the existence of a protein shell around a nucleic acid core in the particles. [ABSTRACT FROM PUBLISHER]