Single twist chiral packing

However, there is a structure consistent with both the required space group and the optical properties. The gyroid surface, which occurs frequently in lipid-water systems, provides such a possibility. If we assume that cholesterol skeletons form rod-like infinite helices, this structure represents an effective three-dimensional packing of such helices. Thus, the rods form a body-centered arrangement as shown in Fig. 5.5. In this structure, there is a helical twist between the rods, in addition to the cholesteric twist within each rod. The h)rperbolic structure is a consequence of the chirality of the esters, which induces torsion into the packing arrangement. A racemic mixture does not exhibit this phase natural cholesteric esters contain a single enantiomer only. 

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