Packing and flexibility changes induced by dehydration. Left column: dehydration of the monoclinic cell (cyan) leads to a decrease in unit-cell volume and a reduction of the β angle to 90°; the latter has the most profound effect, moving one molecule in the asymmetric unit by up to 10 Å. This movement reduces the asymmetric unit to a single molecule in an orthorhombic form (red; symmetry-related mate in grey) and results in the stabilization of several loop regions in which electron density was not visible previously. Note that the axis labels refer to the monoclinic cell. In order to demonstrate the shift in unit cells, the orthorhombic form was re-indexed to match the monoclinic convention. Therefore, for the orthorhombic cell the conversion is a→c and c→a. Right column: cartoon representations of the asymmetric units of the monoclinic versus orthorhombic crystal forms. The Cα chains are shown coloured by B factor, indicating a reduction in flexibility in multiple regions.