Structure of Globin mRNA and mRNA‐Protein Particles

The main advantage of dark‐field electron microscopy is to enhance considerably the contrast, of thin biological specimens. It is thus possible to decrease the amount of stain necessary for visualizing macromolecules. Finer details are visible and stain artefacts are reduced. The method has been used for visualizing mRNA and mRNA‐protein particles from rabbit reticulocytes and from duck erythroblasts. Two preparation methods involving no proteins have been used for the specimen preparation: spreading with glycerol and adhesion on positively charged film. Both species of mRNA and mRNA‐protein particles are linear structures about 170 and 220‐nm long, respectively. On the mRNA‐protein particles the proteins are mainly concentrated in 4 to 7 points along the molecule, but we cannot decide if these proteins are selectively bound on secondary structures of the mRNA.