title: Crystal-state 3D-structural characterization of novel, Aib-based, turn and helical peptides.
abstract: The crystal-state conformations of the hexapeptide amide Pht-(Aib)(6)-NH-C(CH(3))(2)-O-OtBu (7), the hexapeptide Ac-L-aIle-(Aib)(5)-OtBu (6), the pentapeptide Z-(Aib)(3)-L-Glu(OtBu)-Aib-O-(CH(2))(2)-(1)Nap (5), the tetrapeptides Z-(Aib)(2)-L-His(N(tau)-Trt)-Aib-OMe (4 I) and Z-(Aib)(2)-L-Nva-Aib-OtBu (4 II), the tripeptide Pyr-(Aib)(3)-OtBu (3 I), the dipeptide amides Pyr-(Aib)(2)-(4)NH-TEMPO (3 II) and Piv-(Aib)(2)-NH-C(CH(3))(2)-O-OtBu (3 III), and the dipeptides Pht-Aib-betaAc(6)c-OtBu (2 I), Pht-Aib-NH-C(CH(3))(2)-O-OtBu (2 II) and Boc-gGly-mAib-OH (2 III) have been determined by X-ray diffraction analyses. All peptides investigated are characterized by one or more turn/helix forming Aib residues. Except the three short dipeptides, all are folded into C==O...H--N intramolecularly H-bonded 3(10)-helices, or into various types of beta-turns. In the structure of 6, two independent molecules of opposite screw sense were observed in the asymmetric unit, generating diastereomeric 3(10)-helices.
authors.affiliation: Institute of Biomolecular Chemistry, CNR, Department of Chemistry, University of Padova, 35131 Padova, Italy. marco.crisma@unipd.it
authors.forename: Marco
authors.initials: M
authors.lastname: Crisma
authors.forename: Erika
authors.initials: E
authors.lastname: Andreetto
authors.forename: Marta
authors.initials: M
authors.lastname: De Zotti
authors.forename: Alessandro
authors.initials: A
authors.lastname: Moretto
authors.forename: Cristina
authors.initials: C
authors.lastname: Peggion
authors.forename: Fernando
authors.initials: F
authors.lastname: Formaggio
authors.forename: Claudio
authors.initials: C
authors.lastname: Toniolo
mesh_terms: D000621:Aminoisobutyric Acids / Q000737:chemistry*; D003460:Crystallization; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D009842:Oligopeptides / Q000737:chemistry*
chemical_list: D000621:Aminoisobutyric Acids; D009842:Oligopeptides