The electron-dense coating layer lies between the spiral and the membrane. Comparison of side-view sections through knobs in tomograms of schizont material prepared using different methods, showing layered arrangement of spiral, coat layer, and membrane; averages of 10 tomographic slices through the knob apex. (A) High-pressure-frozen, freeze-substituted schizont showing membrane bilayer and underlying electron-dense material. (B) Negative-stained detergent-insoluble schizont skeleton; contrast inverted to match (A) and (C). The path of the spiral coil through the tomogram section is indicated by green circles. Some membrane remains after detergent extraction. View orthogonal to the plane of the tomogram. (C) Schizont skeleton in vitreous ice, showing partially detergent-extracted membrane and underlying electron-dense material. A sharp discontinuity is present at the apex and in the coat layer.