The Trinodular Structure of Fibrinogen: Confirmation by both Shadowing and Negative Stain Electron Microscopy

Fibrinogen molecules sprayed on mica, dried in vacuo and shadowed with platinum appear as trinodular rods. We describe here the flotation technique of negative staining by which we were able to visualize individual fibrinogen molecules. The fibrinogen molecules in our negatively stained preparations have a trinodular structure identical to that of shadowed molecules. The molecules are 45 nm long, the two outer nodules are 6-7 nm in diameter, and the middle nodule is 4-5 nm in diameter. We believe that the 20 nm diameter globules seen in previous negative staining studies are aggregates of these molecules.