title: Vibrational CD studies of interchain hydrogen-bonded tripodal peptides.
abstract: The solution conformations of three trispeptides--L,L,L-1,3,5-C6H3[CH2NHCOCH(X)-NHBoc++ +]3, X = CH3 (Ala) or CH2CH(CH3)2 (Leu), and L,L,L-N(CH2CH2NHCOCH[CH2-CH(CH3)2]NHBoc)3--have been determined from their ir and vibrational CD (VCD) spectra in the NH stretching and carbonyl stretching regions in apolar solution. The compounds containing L-Leu are shown to occur primarily in a propeller conformation with C3 symmetry that is stabilized by interchain hydrogen bonds. Through application of the coupled oscillator model of VCD, a right-handed sense for the hydrogen-bonded chains in the propeller is deduced, in agreement with previous empirical force field calculations. The spectra also provide evidence for interchain association between two chains, resulting in a C10-ring. For chains not involved in interchain association, the spectra reveal the presence of C7-rings within a chain. The trispeptide containing L-Ala is found to occur primarily in a random form.
authors.affiliation: Department of Chemistry Syracuse University, New York 13244-4100.
authors.forename: M G
authors.initials: MG
authors.lastname: Paterlini
authors.forename: T B
authors.initials: TB
authors.lastname: Freedman
authors.forename: L A
authors.initials: LA
authors.lastname: Nafie
authors.forename: Y
authors.initials: Y
authors.lastname: Tor
authors.forename: A
authors.initials: A
authors.lastname: Shanzer
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D006860:Hydrogen Bonding; D007202:Indicators and Reagents; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D014732:Vibration
chemical_list: D007202:Indicators and Reagents; D009842:Oligopeptides