title: Crystal structure of a tripeptide containing aminocyclododecane carboxylic acid: a supramolecular twisted parallel β-sheet in crystals.
abstract: The crystal structure of a tripeptide Boc-Leu-Val-Ac12 c-OMe (1) is determined, which incorporates a bulky 1-aminocyclododecane-1-carboxylic acid (Ac12 c) side chain. The peptide adopts a semi-extended backbone conformation for Leu and Val residues, while the backbone torsion angles of the C(α,α) -dialkylated residue Ac12 c are in the helical region of the Ramachandran map. The molecular packing of 1 revealed a unique supramolecular twisted parallel β-sheet coiling into a helical architecture in crystals, with the bulky hydrophobic Ac12 c side chains projecting outward the helical column. This arrangement resembles the packing of peptide helices in crystal structures. Although short oligopeptides often assemble as parallel or anti-parallel β-sheet in crystals, twisted or helical β-sheet formation has been observed in a few examples of dipeptide crystal structures. Peptide 1 presents the first example of a tripeptide showing twisted β-sheet assembly in crystals.
authors: Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
authors: Prema G
authors: PG
authors: Vasudev
authors: Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
authors: Subrayashastri
authors: S
authors: Aravinda
authors: Department of Physics, Indian Institute of Science, Bangalore, 560012, India.
authors: Narayanaswamy
authors: N
authors: Shamala
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D006844:Hydrocarbons, Cyclic / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D008958:Models, Molecular; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: C405283:1-aminocyclododecane-1-carboxylic acid; D006844:Hydrocarbons, Cyclic; D009842:Oligopeptides
keywords: 1-aminocyclododecane-1-carboxylic acid; crystal structure; tripeptide; twisted β-sheet