title: Effects of thioamide substitution for the enkephalin conformation. Crystal structure of Boc-Tyr-Gly-Gly-Phe psi [CSNH]Leu-OBzl.
abstract: The crystals of Boc-Tyr-Gly-Gly-Phe psi[CSNH]Leu-OBzl monohydrate (C40H51N5O8S.H2O), a monothionated Leu-enkephalin analogue, were obtained with space group P2(1), a = 12.616(3), b = 9.347(2), c = 18.548(5) A, beta = 96.31(4) degrees. The structure was elucidated by X-ray diffraction analysis, and refined to the R value of 0.091 for the observed 3294 reflections. Two antiparallel molecules related by a pseudo twofold symmetry were stabilized to each other by four intermolecular hydrogen bonds. The molecular conformation was bent at the Phe residue, and the extended moiety of the Tyr-Gly-Gly fragment was almost perpendicular to that of the Phe-Leu residues. Consequently the molecule, as a whole, formed an L-shape conformation with a slightly left-handed helicity.
authors.affiliation: Osaka University of Pharmaceutical Sciences, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Doi
authors.forename: S
authors.initials: S
authors.lastname: Takehara
authors.forename: T
authors.initials: T
authors.lastname: Ishida
authors.forename: M
authors.initials: M
authors.lastname: Inoue
mesh_terms: D000577:Amides; D000595:Amino Acid Sequence; D004743:Enkephalin, Leucine / Q000031:analogs & derivatives*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012984:Software; D013854:Thioamides; D014961:X-Ray Diffraction
chemical_list: D000577:Amides; D013854:Thioamides; C062623:t-butyloxycarbonyltyrosyl-glycyl-glycyl-phenylalanyl-psi(thioamide)leucyl benzyl ester; D004743:Enkephalin, Leucine