Electron microscopy analysis of β₂GPI. Purified human plasma β₂GPI was visualized with electron microscopy. (A-D) Magnifications of purified plasma β₂GPI show a circular conformation. (E-H) Representation of panels A through D, respectively. (I-L) Purified plasma β₂GPI in the presence of antibodies directed against domain I of β₂GPI shows on magnification an open fishhook-like shape of β₂GPI. (M-P) Representation of panels I through L, respectively.