Hao ( 16 ), described by Nowick et al., has been frequently used in combination with oligourea templates ( 8 )[ 171 ] or ornithine amino acids that act as δ-sided turns.[ 172 ] Moreover, Hao ( 16 ) and other moieties also proved useful for the initiation of intermolecular β-sheet formation.[ 173, 174 ] Hamilton and co-workers used a diphenylacetylene moiety ( 17 ) to arrange two strands in an antiparallel β-sheet.[ 166 ] This moiety concomitantly replaces one residue in each strand, thereby reproducing the distinctive interstrand hydrogen bonds of a β-sheet structure and incorporating a covalent cross-link between the two strands.
Source: wiktionary