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Figure 10
(a) The C2 unit cell with two bilayers for L-Nle at 100 K. H atoms are omitted, hydrogen bonds are dotted. Molecules B (pink), C (light pink), E (light grey) and F (white) have the same side-chain conformation, but B and E are tilted slightly to relieve close contacts (double arrows) with A (purple) and D (blue). The two hydrophobic regions in the unit cell (grey shades) are related by the central twofold rotation axis. (b) Comparison of the 100 K cell (black edges) with the commensurate supercell (orange) and the unit cell at 210 K (purple). (c) The three possible types of bilayers with a 2:1 conformational distribution between trans, trans, trans (light molecules) and trans, gauche+, trans (dark molecules). Type 3 (grey and black molecules) has not been observed experimentally. Red and blue shadings in (b) highlight type 1 and type 2 bilayers and the 1–2–1–2 stacking sequence along the c-axis (arrows).

IUCrJ
Volume 3| Part 5| September 2016| Pages 341-353
ISSN: 2052-2525
doi:10.1107/S2052252516010472