Atomic force microscopy (AFM) setup. (A) AFM schematic. (B) Functionalization of AFM. Molecules depicted represent a composite of 2 sets adsorbed or captured on the AFM tip or the polystyrene dish. A1A2A3 tridomain was directly adsorbed or captured by anti-His mAb preadsorbed on the surface. GPIbα or CR1 was adsorbed on the cantilever tip. (C) Binding specificity. Immobilized A1A2A3 bound GPIbα- or CR1-coated cantilever tips but not BSA-coated tips. ND indicates not done. GPIbα did not bind captured A1A2A3 probably because of its different conformation from adsorbed A1A2A3.