title: L-alanyl-L-alanyl-L-alanine: parallel pleated sheet arrangement in unhydrated crystal structure, and comparisons with the antiparallel sheet structure.
abstract: The tripeptide L-alanyl-L-alanyl-L-alanine has been crystallized from a water/dimethylformamide solution in an unhydrated form, with cell dimensions a = 11.849, b = 10.004, c = 9.862 A, beta = 101.30 degrees, monoclinic space group P21 with 4 molecules per cell (2 independent molecules in the asymmetric unit). The structure was determined by direct methods and refined to a discrepancy index R = 0.057. The tri-L-alanine molecules are packed in a parallel pleated sheet arrangement with unusually long amide nitrogen-carbonyl oxygen contacts within sheets. Comparisons are made with the antiparallel pleated sheet structure of tri-L-alanine hemihydrate, previously crystallized from the same solvent system.
authors.affiliation: Biochemistry Department, University of Toronto, Ontario, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Hempel
authors.forename: N
authors.initials: N
authors.lastname: Camerman
authors.forename: A
authors.initials: A
authors.lastname: Camerman
mesh_terms: D000595:Amino Acid Sequence; D004126:Dimethylformamide / Q000737:chemistry; D006860:Hydrogen Bonding; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry*; D011487:Protein Conformation; D014867:Water / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D046911:Macromolecular Substances; D009842:Oligopeptides; D014867:Water; C039944:alanyl-alanyl-alanine; D004126:Dimethylformamide