High- and low-pitch helical structures of tilted chiral lipid bilayers

Molecular packing in helical ribbons of tilted chiral lipid bilayers is investigated as cholesteric liquid crystals. Two types of helices with high- and low-pitch angles observed in the pathway for cholesterol crystallization (ChC) in native and model biles by Chung ed nl. [Proc. Natl. Acad. Sci. U.S.A. 90, 11341 (1993)] correspond to parallel and antiparallel packing of molecules at the edges of the ribbon, respectively. The structural change in the ChC is explained as a decreasing succession of free energy of the metastable intermediate structures.