title: The crystal structure of Z-(Aib)10-OH at 0.65 Å resolution: three complete turns of 310-helix.
abstract: The synthetic peptide Z-(Aib)10-OH was crystallized from hot methanol by slow evaporation. The crystal used for data collection reflected synchrotron radiation to sub-atomic resolution, where the bonding electron density becomes visible between the non-hydrogen atoms. Crystals belong to the centrosymmetric space group P1. Both molecules in the asymmetric unit form regular 310 -helices. All residues in each molecule possess the same handedness, which is in contrast to all other crystal structure determined to date of longer Aib-homopeptides. These other peptides are C-terminal protected by OtBu or OMe. In these cases, because of the missing ability of the C-terminal protection group to form a hydrogen bond to the residue i-3, the sense of the helix is reversed in the last residue. Here, the C-terminal OH-groups form hydrogen bonds to the residues i-3, in part mediated by water molecules. This makes Z-(Aib)10-OH an Aib-homopeptide with three complete 310-helical turns in spite of the shorter length it has compared with Z-(Aib)11-OtBu, the only homopeptide to date with three complete turns.
authors.affiliation: IMBB/FORTH, 70013, Iraklion Crete, Greece.
authors.forename: Renate
authors.initials: R
authors.lastname: Gessmann
authors.affiliation: Department of Food Sciences, Interdisciplinary Research Center, Justus-Liebig-University of Giessen, 35392, Giessen, Germany.
authors.forename: Hans
authors.initials: H
authors.lastname: Brückner
authors.affiliation: IMBB/FORTH, 70013, Iraklion Crete, Greece.
authors.forename: Kyriacos
authors.initials: K
authors.lastname: Petratos
mesh_terms: D000621:Aminoisobutyric Acids / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008958:Models, Molecular; D017433:Protein Structure, Secondary
chemical_list: D000621:Aminoisobutyric Acids; C100049:2-aminoisobutyric acid
keywords: 310-helix; achiral peptide; centrosymmetry; left-handed helix; sub-atomic resolution; three complete turns; unprotected peptide; α-aminoisobutyric acid