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Conformations of dehydrophenylalanine containing peptides: nmr studies of an acyclic hexapeptide with two Δ z ‐Phe residues
Author(s) -
Chauhan V. S.,
Uma K.,
Kaur Paramjeet,
Balaram P.
Publication year - 1989
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360280306
Subject(s) - chemistry , solvent , stereochemistry , crystallography , peptide , nuclear overhauser effect , population , nuclear magnetic resonance spectroscopy , organic chemistry , biochemistry , demography , sociology
The conformation of an acyclic dehydrophenylalanine (Δ z ‐Phe) containing hexapeptide, Boc‐Phe‐Δ z ‐Phe‐Val‐Phe‐Δ z ‐Phe‐Val‐OMe, has been investigated in CDCl 3 and (CD 3 ) 2 SO by 270‐MHz 1 H‐nmr. Studies of NH group solvent accessibility and observation of interresidue nuclear Overhauser effects (NOEs) suggest a significant solvent‐dependent conformational variability. In CDCl 3 , 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 N i H ⟷ N i+1 H NOEs. Evidence is also obtained for conformational heterogeneity from the detection of some C i α H ⟷ N i+1 H NOEs characteristic of extended strands. In (CD 3 ) 2 SO, the peptide largely favors an extended conformation, characterized by five solvent‐exposed NH groups and successive C i α H ⟷ N i+1 H NOEs for the L ‐residues and C i β H ⟷ N i+1 H NOEs for the Δ z ‐Phe residues. The results suggest that Δ z ‐Phe residues do not provide compelling conformational constraints.