Figure 1.

Crystal packing. (a) The asymmetric unit of the C222₁ crystal form viewed down the non-crystallographic three-fold axis of the central hexamer. The flanking hexamers are located around the central hexamer at an angle of ~110°. The local non-crystallographic three-fold axis of the two outer hexamers is almost orthogonal to the central non-crystallographic three-fold axis. The zinc atoms are illustrated as large spheres to mark the position of the three-fold axes. The hexamers are numbered from I to III. (b) The crystal packing in the C222₁ space group drawn with main chain trace with the asymmetric unit in magenta. (c) The crystal packing of the human insulin in space group C2. The asymmetric unit molecule is colored magenta. The inserts in (b) and (c) show crystals of the C222₁ and C2 forms, respectively.