title: Unusual conformational preferences of beta-alanine containing cyclic peptides. VII.
abstract: In the present paper we describe the synthesis, purification, and single crystal x-ray analysis of the cyclic pentapeptide cyclo-(Pro-Phe-Phe-beta-Ala-beta-Ala). This compound crystallizes in the orthorhombic space group P2I2I2I from methanol and adopts in the solid state an unusual conformation characterized by a cis beta-Ala5-Pro1 peptide bond and by an intramolecular hydrogen bond stabilizing a C11-and a C12-ring structure. The C11 structure contains the Phe3 and the beta-Ala4 at the corner position of the turn; it is the first observation of a type II beta-turn enlargement due to the insertion of an extra methylene group of the beta-alanine residue. The rest of the molecule participates in a newly characterized C12-ring structure, which incorporates a beta-Ala residue at position i of the turn.
authors.affiliation: Centro Interdipartimentale di Ricerca su Peptidi Bioattivi, University of Naples Federico II, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Lombardi
authors.forename: M
authors.initials: M
authors.lastname: Saviano
authors.forename: F
authors.initials: F
authors.lastname: Nastri
authors.forename: O
authors.initials: O
authors.lastname: Maglio
authors.forename: M
authors.initials: M
authors.lastname: Mazzeo
authors.forename: C
authors.initials: C
authors.lastname: Pedone
authors.forename: C
authors.initials: C
authors.lastname: Isernia
authors.forename: V
authors.initials: V
authors.lastname: Pavone
mesh_terms: D000595:Amino Acid Sequence; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry*; D011487:Protein Conformation; D015091:beta-Alanine / Q000032:analysis*
chemical_list: D010456:Peptides, Cyclic; D015091:beta-Alanine