Figure 2.

Stereographic projection of the self-rotation function in spherical polar angles at κ = 180° for the hATX crystal. A self-rotation search was carried out with the program POLARRFN from the CCP4 suite (Collaborative Computational Project, Number 4, 1994 ▶) using the data in the 30.0–3.0 Å resolution shell and an integration radius of 30.0 Å. The two strongest peaks [relative height of 100, (ω, ϕ) = (90.0, 90.0°) and (90.0, −90.0°)] indicate the crystallographic twofold symmetry (origin peak). Contour lines are drawn at an increment of 10% of the origin peak. The program produces a constant rotation angle κ for different axis directions defined by ω (the angle from the pole) and ϕ (the angle around the equator). The ϕ angles are marked on the circumference and the ω angles are defined as 0° or 180° at the centre and 90° around the edge. Noncrystallographic twofold rotation axes (91% height of the origin peak) are found at (ω, ϕ) = (57.3, 0.0°) and (147.3, 0.0°).