Transmission electron microscopy of individual fibrinogen molecules. Recombinant fibrinogen is shown in (A) and plasma fibrinogen is shown in (B). The arrows indicate a fourth nodule (made up by the C termini of Aα chains), present on some molecules within a representative field. The smaller panels contain molecules selected to illustrate the various structures with four nodules. All pictures are at the same magnification (60,000×) and the bar in (B) indicates 100 nm.