title: Conformation for a beta-cyclodextrin monosubstituted with a cyclic dipeptide.
abstract: The structural characterization of a beta-cyclodextrin monosubstituted with the peptide cyclo(L-His-L-Leu) is reported. This work provides an x-ray example of a covalently bound group that folds in such a way that the terminal apolar side chain is retained in the hydrophobic interior of the cone-shaped cyclodextrin cavity. 6-Deoxy-6-cyclo(L-histidyl-L-leucyl)-beta-cyclodextrin crystallizes in the space group P1 with cell dimensions a = 14.728(8) A, b = 15.084(7) A, c = 18.182(10) A, alpha = 94.36(6) degrees, beta = 95.81(5) degrees, gamma = 116.08(9) degrees; overall isotropic agreement R = 10.6% for 5703 observed reflections (Fo greater than 3 sigma). The molecular structure consists of two independent molecules with the formula C54H86N4O36.7.25H2O. Each molecule assumes a "sleeping swan"-like overall shape with the hydrophobic leucine side chain inserted inside the cavity of the macrocycle. The two independent units give rise to a head-to-tail dimer linked by hydrogen bonds occurring between primary and secondary hydroxyl groups of the two monomers. The packing of the dimers produces cavities containing water molecules. There are infinite hydrophilic channels running in the crystal, which is similar to what is found in the structures of cyclic peptides.
authors.affiliation: Dipartimento di Chimica, Università di Napoli, Italy.
authors.forename: B
authors.initials: B
authors.lastname: Di Blasio
authors.forename: V
authors.initials: V
authors.lastname: Pavone
authors.forename: F
authors.initials: F
authors.lastname: Nastri
authors.forename: C
authors.initials: C
authors.lastname: Isernia
authors.forename: M
authors.initials: M
authors.lastname: Saviano
authors.forename: C
authors.initials: C
authors.lastname: Pedone
authors.forename: V
authors.initials: V
authors.lastname: Cucinotta
authors.forename: G
authors.initials: G
authors.lastname: Impellizzeri
authors.forename: E
authors.initials: E
authors.lastname: Rizzarelli
authors.forename: G
authors.initials: G
authors.lastname: Vecchio
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D003505:Cyclodextrins / Q000737:chemistry*; D004151:Dipeptides / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010456:Peptides, Cyclic / Q000737:chemistry*; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction; D047392:beta-Cyclodextrins
chemical_list: D003505:Cyclodextrins; D004151:Dipeptides; D010456:Peptides, Cyclic; D047392:beta-Cyclodextrins; C075907:6-deoxy-6-cyclo(histidyl-leucyl)cyclodextrin; C075906:cyclo(histidyl-leucyl); C031215:betadex