Electron microsocpy of plasmic fragments of human fibrinogen as related to trinodular structure of the intact molecule.

We have examined rotary shadowed, purified plasmic fragments of human fibrinogen with the electron microscope and have determined the relation of these fragments to the intact fibrinogen molecule. Both intact fibrinogen and its earliest cleavage product, fragment X, are trinodular. The next largest product, fragment Y, consists of two linked nodules. The two terminal products, fragments D and E, are single nodules. From measurements of simultaneously shadowed specimens of these different species, we conclude that the outer nodules of the trinodular fibrinogen molecule are the fragment D-containing regions and the central nodule is the fragment E-containing region.