The Φ-values mapped onto the native structure of FADD DD. High Φ-values (≥ 0.51) are shown in blue, medium Φ-values (0.16–0.5) are shown in magenta and low Φ-values (≤ 0.15) are shown in red. The Ala to Gly scanning surface mutations are shown by colouring the ribbon, the buried residues mutated are shown as spheres. (a and b) The Φ-values of the three helix bundles from different faces of the molecule. (c and d) The Φ-values of the central core from different faces. H3 and H6 have been removed to allow a clear view. In c, H6 would be facing the viewer; in (d) H3 would be facing the viewer.