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RNA of high molecular weight was isolated from fresh calf livers and studied electron-microscopically by means of spraying-shadowing method. The RNA molecules were found polymorphic, but grossly classified into two categories; the longer rod-like ones and the shorter, rather oval ones. The dimension of the former was about 1,000 Å in length, 40–50 Å in width and about 30 Å in thickness, its molecular weight estimates from the dimension being about 1.2×10. This value was in good agreement with the sedimentation-viscosity molecular weight of the 26 S component found by ultracentrifugal analysis. The latter component was supposed to correspond to the 16 S component found by ultracentrifugation. [ABSTRACT FROM PUBLISHER]

Ribosomes from beef brain cortex were purified and examined in an electron microscope and in a ultracentrifuge. The ultraviolet absorption spectrum indicated the ribonucleoprotein character of the ribosome preparation. The nearly constant ratio of RNA/protein was found to be close to 50/50. The preparation of brain cortex ribosomes was characterized by the sedimentation coefficients of 120 s, 80 s, 60 s and 40 s. Electron microscope observations showed the different forms of brain ribosomes, of which stability depended on the Mg concentration of the medium. A 80 s particle could dissociate to form a 60 s particle and a 40 s particle. [ABSTRACT FROM PUBLISHER]

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]