title: Nuclear magnetic resonance studies on a cyclic dodecapeptide analogue of a repeat hexapeptide of tropoelastin: evaluation of secondary structure.
abstract: The cyclododecapeptide, (Ala1-Pro2-Gly3-Val4-Gly5-Val6)2, was synthesized and its secondary structure was evaluated from extensive studies in dimethyl sulphoxide, trifluoroethanol and water using NMR methods. A selective decoupling technique in 13C-NMR has been utilized in order to assign the C=O carbon resonances. Temperature dependence of the peptide NH protons and the solvent perturbation of the peptide NH and C=O resonances show the occurrence in all solvents of a beta-turn (a 10-membered H-bond between the Val4 NH and Ala1 C=O) and a gamma-turn, an 11-membered H-bond between the Gly3 NH and the Gly5 C=O; and a possible 14-membered H-bond between the Ala1 NH and the Val4 C=O in dimethyl sulphoxide and trifluoroethanol. These secondary structural features are compared with the linear polyhexapeptide and found the the beta-turn and the gamma-turn are the common conformational features of these peptide systems.
mesh_terms: D000595:Amino Acid Sequence; D055598:Chemical Phenomena; D002621:Chemistry; D004549:Elastin / Q000031:analogs & derivatives; D009682:Magnetic Resonance Spectroscopy; D010446:Peptide Fragments; D010456:Peptides, Cyclic / Q000138:chemical synthesis; D014333:Tropoelastin
chemical_list: D010446:Peptide Fragments; D010456:Peptides, Cyclic; D014333:Tropoelastin; D004549:Elastin