Transmission electron microscopy of αIIbβ3-fibrinogen complexes formed in the presence of Mn²⁺. (A) Separate αIIbβ3 and fibrinogen molecules. (B-C) Bimolecular and trimolecular complexes of αIIbβ3 and fibrinogen. It is noteworthy that the αIIbβ3 molecules involved in these complexes all were in the open conformation. (D) Fibrinogen bound to an αIIbβ3 oligomer. Magnification, × 170 000.