Conformations of dehydrophenylalanine containing peptides: nmr studies of an acyclic hexapeptide with two Δz-Phe residues
✍ Scribed by V. S. Chauhan; K. Uma; Paramjeet Kaur; P. Balaram
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1989
- Tongue
- English
- Weight
- 478 KB
- Volume
- 28
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
The conformation of an acyclic dehydrophenylalanine ( A'-Phe) containing hexapeptide, Boc-Phe-A'-Phe-Val-Phe-A'-Phe-Val-OMe, has been investigated in CDCl, and (CD,),SO by 270-MHz 'H-nmr. Studies of NH group solvent accessibility and observation of interresidue nuclear Overhauser effects (NOEs) suggest a significant solvent-dependent conformational variability. In CDCI,, 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,H -N,+,H NOEs. Evidence is also obtained for conformational heterogeneity from the detection of some CPH -N,+ ,H NOES characteristic of extended strands. In (CD,),SO, the peptide largely favors an extended conformation, characterized by five solvent-exposed NH groups and successive CPH -N,+'H NO% for the L-residues and CPH -N,+,H NOES for the A'-Phe residues. The results suggest that Az-Phe residues do not provide compelling conformational constraints.