title: Difference in the structures of alanine tri- and tetra-peptides with antiparallel β-sheet assessed by X-ray diffraction, solid-state NMR and chemical shift calculations by GIPAW.
abstract: Alanine oligomers provide a key structure for silk fibers from spider and wild silkworms.We report on structural analysis of L-alanyl-L-alanyl-L-alanyl-L-alanine (Ala)4 with anti-parallel (AP) β-structures using X-ray and solid-state NMR. All of the Ala residues in the (Ala)4 are in equivalent positions, whereas for alanine trimer (Ala)3 there are two alternative locations in a unit cell as reported previously (Fawcett and Camerman, Acta Cryst., 1975, 31, 658-665). (Ala)4 with AP β-structure is more stable than AP-(Ala)3 due to formation of the stronger hydrogen bonds. The intermolecular structure of (Ala)4 is also different from polyalanine fiber structure, indicating that the interchain arrangement of AP β-structure changes with increasing alanine sequencelength. Furthermore the precise (1)H positions, which are usually inaccesible by X-ray diffraction method, are determined by high resolution (1)H solid state NMR combined with the chemical shift calculations by the gauge-including projector augmented wave method.
authors.affiliation: Department of Biotechnology, Tokyo University of Agriculture and Technology, 2-24-16 Koganei, Tokyo, Japan; Institute for Molecular Science, 38 Nishigo-Naka, Myodaiji, Okazaki 444-8585, Japan.
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Asakura
authors.forename: Koji
authors.initials: K
authors.lastname: Yazawa
authors.forename: Kumiko
authors.initials: K
authors.lastname: Horiguchi
authors.forename: Furitsu
authors.initials: F
authors.lastname: Suzuki
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nishiyama
authors.forename: Katsuyuki
authors.initials: K
authors.lastname: Nishimura
authors.forename: Hironori
authors.initials: H
authors.lastname: Kaji
mesh_terms: D000409:Alanine / Q000737:chemistry; D000818:Animals; D060126:Characidae; D009682:Magnetic Resonance Spectroscopy; D010455:Peptides / Q000737:chemistry; D047011:Silk / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D010455:Peptides; D047011:Silk; D000409:Alanine
keywords: GIPAW; alanine oligopeptide; antiparallel β-sheet; solid state NMR