Morphology of VSV embedded in vitreous ice. (A) At pH 7.5, G forms a thin continuous layer around the viral particle. The arrows indicate viruses with no G visible at their base. (B) At pH 6, G elongates and individual spikes protruding from the membrane are visible. The arrow indicates an area in which the spikes are regularly organized. (C) At pH 5.5, all the spikes display a well-ordered helical organization. Note that the membrane at the base of the particle is disrupted, allowing the release of internal material (indicated by arrows). In A and B, the image is underfocused by ∼1.8 µm. In C, it is underfocused by 3 µm, to improve visualization of the helical G array.