title: Inversion of 3(10)-helix screw sense in a (D-alpha Me)Leu homo-tetrapeptide induced by a guest D-(alpha Me)Val residue.
abstract: The terminally blocked tetrapeptide pBrBz-[D-(alpha Me)Leu]2-D-(alpha Me)Val-D-(alpha Me)Leu-OfBu is folded in the crystal state in a left-handed 3(10)-helical structure stabilized by two consecutive 1<--4 C = O...H-N intramolecular H-bonds, as determined by X-ray diffraction analysis. A CD study strongly supports the view that this conformation is also that largely prevailing in MeOH solution. A comparison with the published conformation of pBrBz-[D-(alpha Me)Leu]4-OfBu indicates that incorporation of a single internal beta-branched (alpha Me)Val guest residue into the host homo-tetrapeptide from the gamma-branched (alpha Me)Leu residue is responsible for a dramatic structural perturbation, i.e. an inversion of the 3(10) screw sense from right to left-handed.
authors.affiliation: Department of Organic Chemistry, University of Padova, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Formaggio
authors.forename: M
authors.initials: M
authors.lastname: Crisma
authors.forename: C
authors.initials: C
authors.lastname: Toniolo
authors.forename: E
authors.initials: E
authors.lastname: Benedetti
authors.forename: B
authors.initials: B
authors.lastname: Di Blasio
authors.forename: M
authors.initials: M
authors.lastname: Saviano
authors.forename: S
authors.initials: S
authors.lastname: Galdiero
authors.forename: J
authors.initials: J
authors.lastname: Kamphuis
authors.forename: A
authors.initials: A
authors.lastname: Santini
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008745:Methylation; D008958:Models, Molecular; D015394:Molecular Structure; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary
chemical_list: C107985:4-bromobenzoyl-(methylleucine)2-methylvaline-methyleucine-tert-butoxy ester; D009842:Oligopeptides