title: Characteristic molecular packing in the crystal structure of tert-butoxycarbonyl-L-phenylalanyl-L-methionine methyl ester.
abstract: The molecular conformation and association of the peptide Boc-L-Phe-L-Met-OMe have been studied in the solid state by X-ray diffraction. The peptide crystallizes in the orthorhombic system, space group P2(1)2(1)2(1), with cell parameters of a = 9.821(2), b = 25.394(6), c = 28.714(8) A, V = 7161(3) A3. The structure has been solved by direct methods and refined to a final R of 0.079 for 5464 independent reflections with Fo > or = sigma(Fo). The crystal consists of three independent molecular conformations per asymmetric unit. Respective peptide backbones adopt an extended conformation with the side-chains of Phe and Met residues being arranged below and above the backbone chains. Contrary to the sheet structure most frequently observed in the crystal packing of the extended peptide conformations, three independent molecules lie spirally along the c-axis and form a pin-wheel-like crystal packing. The sheet structures formed by two of three independent molecules are almost at right angles to the backbone of the remaining molecule. This molecular packing mode would provide a possible interaction model between the intersecting beta-sheet structure and single-strand structure of polypeptide.
authors.affiliation: Osaka University of Pharmaceutical Sciences, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Doi
authors.forename: Y
authors.initials: Y
authors.lastname: In
authors.forename: M
authors.initials: M
authors.lastname: Inoue
authors.forename: T
authors.initials: T
authors.lastname: Ishida
mesh_terms: D000595:Amino Acid Sequence; D018360:Crystallography, X-Ray; D004151:Dipeptides / Q000737:chemistry*; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D015394:Molecular Structure
chemical_list: D004151:Dipeptides; C092914:tert-butoxycarbonyl-phenylalanyl-methionine methyl ester