Assessment of PF4/heparin complexes by AFM. Representative liquid AFM tapping mode images of (A) PF4 alone and (B) PF4/UFH, (C) PF4/HO16, (D) PF4/HO08, (E) PF4/HO06, and (F) PF4/fondaparinux complexes on mica; the corresponding height histograms derived from all experiments are shown in G.