Figure 2.
Crystal structures of macrocyclic peptides mcVQIVFBr, mcAIIFL and mcLVFFA. Within the monomeric structures (a), hydrogen bonds link the blocking and recognition strands and are shown as dotted lines. β-Sheet formation by dimeric assemblies are either parallel or antiparallel as shown in (b). (c) Molecular packing of four different tetramers. The tetrameric macrocyclic molecules form a variety of β-sheet-to-β-sheet packing geometries, deviating by 0° to 45° from cross-β geometry as shown in (d).