The asymmetric units of the new crystal forms. (a) The three chains of the C2 asymmetric unit (A, B and E) are shown in cyan, and the symmetry-related chains that form the biological dimers are shown in gray (sB, sA and sE). (b) The four chains of the P21 asymmetric unit (A, B, C and D) are shown in green. (c) The six chains of the P21 ‘big’ asymmetric unit (A, B, C, D, E and F) are shown in red.