Detalle de: Design, synthesis, and structural analysis of turn modified cyclo-(αβ3αβ2α)2 peptide derivatives toward crystalline hexagon-shaped cationic nanochannel assemblies

Intrigued by the not fully extended hairpin monomeric structure of the previously reported cyclo -(αβ 3 αβ 2 α) 2 peptide 2, as well as its nanochannel crystallographic assembly, we here investigate the structural properties of a series of turn derivatives ( 3 – 17 ). Five crystallographic monomeric structures of the symmetric and asymmetric cyclo -(αβ 3 αβ 2 α) 2 peptides 3 – 17 are found; the novel saddlelike ( 4 and 16 ) and the twisted hairpin ( 6 ) conformers, as well as the not fully extended hairpins 7 and 14 . The pentafluorophenyl/1-naphthyl and pentafluorophenyl/9-phenanthryl derivatives 7 and 14, respectively, adopt the anticipated hexagon-shaped crystalline nanotube assemblies, resembling the crystal packing of the parent peptide 2 . The structural analysis of the compounds as described here can serve as a basis for biological applications, such as the design of β-sheet mimics or for the development of functional nanomaterials.