title: Protected 1-3 segment of the peptaibol antibiotics alamethicin and hypelcin. Solid-state and solution study of a stereochemically constrained linear peptide.
abstract: A study of the modes of folding and self-association of Z-Aib-L-Pro-Aib-OMe (the protected 1-3 segment of the peptaibol antibiotics alamethicin and hypelcin) in the solid state was performed using i.r. absorption and X-ray diffraction. The stereochemically constrained tripeptide molecules adopt a 4 leads to 1 intramolecularly H-bonded form (beta-turn), where the single intramolecular H-bond is found between the peptide N-H group of the Aib3 residue and the urethane C = O group of the N-blocking benzyloxycarbonyl moiety. This folded structure is stabilized by an intermolecular H-bond between the urethane N-H group of the Aib1 residue and the peptide C = O group of the Pro2 residue of a symmetry related molecule. According to the i.r. absorption data, in CH2Cl2 and TMP solutions the same intramolecularly H-bonded form occurs as that found in solid state. Compared to the situation in the solid state, in CH2Cl2 and TMP solvation of the urethane N-H group replaces self-association (through the same N-H group). The results are also discussed in relation to those obtained for other protected -Aib-X-Aib- (X = Aib, L-Ala, L-Val) tripeptide segments of peptaibol antibiotics.
mesh_terms: D000408:Alamethicin / Q000031:analogs & derivatives; D000900:Anti-Bacterial Agents; D006860:Hydrogen Bonding; D007202:Indicators and Reagents; D008958:Models, Molecular; D009842:Oligopeptides; D010446:Peptide Fragments; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; D007202:Indicators and Reagents; D009842:Oligopeptides; D010446:Peptide Fragments; D000408:Alamethicin; C025478:hypelcin A