title: Conformations of dehydrophenylalanine containing peptides: nmr studies of an acyclic hexapeptide with two delta Z-Phe residues.
abstract: The conformation of an acyclic dehydrophenylalanine (delta Z-Phe) containing hexapeptide, Boc-Phe-delta Z-Phe-Val-Phe-delta Z-Phe-Val-OMe, has been investigated in CDCl3 and (CD3)2SO by 270-MHz 1H-nmr. Studies of NH group solvent accessibility and observation of interresidue nuclear Overhauser effects (NOEs) suggest a significant solvent-dependent conformational variability. In CDCl3, a population of folded helical conformations is supported by the inaccessibility to solvent of the NH groups of residues 3-6 and the detection of several NiH----Ni + 1H NOEs. Evidence is also obtained for conformational heterogeneity from the detection of some Ci alpha H----Ni + 1H NOEs characteristic of extended strands. In (CD3)2SO, the peptide largely favors an extended conformation, characterized by five solvent-exposed NH groups and successive Ci alpha H----Ni + 1H NOEs for the L-residues and Ci beta H----Ni + 1H NOEs for the delta Z-Phe residues. The results suggest that delta Z-Phe residues do not provide compelling conformational constraints.
authors.forename: V S
authors.initials: VS
authors.lastname: Chauhan
authors.forename: K
authors.initials: K
authors.lastname: Uma
authors.forename: P
authors.initials: P
authors.lastname: Kaur
authors.forename: P
authors.initials: P
authors.lastname: Balaram
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D009842:Oligopeptides; D010649:Phenylalanine / Q000031:analogs & derivatives*; D011487:Protein Conformation
chemical_list: D009842:Oligopeptides; D010649:Phenylalanine; C018632:phenyldehydroalanine