AFM derived measurement of the dimensions of the knob structures on the IE membrane. Force microscopy was carried out on unfixed, air dried IE. A. AFM tapping mode image of a single trophozoite-IE (FCR3). The boxed insert indicates the two knob structures analysed at higher resolution. B. Higher resolution scan data from the two knobs boxed in Figure 5A, bisected by the red sectioning line with the knob centre and a selected circumferential point indicated by the blue points. C. Two-colour enhanced three dimensional imaging of tapping-mode scan data. D. Topology measurements of the surface bisected by the red line shown in Figure 5B.