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http://nopr.niscpr.res.in/handle/123456789/15329| Title: | Conformational study of peptides containing dehydrophenylalanine Helical structures without hydrogen bond |
| Authors: | Nandel, Fateh S Kaur, Harpreet Malik, Nandita Shankar, Neelaabh Jain, Dharam V S |
| Issue Date: | Dec-2001 |
| Publisher: | NISCAIR-CSIR, India |
| Abstract: | The conformational behaviour of ∆zPhe has been
investigated in the model dipeptide Ac-∆z Phe-NHMe and in the model tripeptides
Ac-X-∆z Phe-NHMe with X=Gly,
Ala,Val, Leu, Abu, Aib and Phe
and is found to be quite different. In the model tripeptides with X=Ala, Val, Leu, Abu, Phe
the most stable structure corresponds to  1=-30°,
ψ1= 120° and 2=ψ2 =30°. This structure is stabilized by the hydrogen bond formation
between C=O of acetyl group and the NH of the amide group, resulting in the
formation of a 10-membered ring but not a 310 helical structure. In
the peptides Ac- Aib-∆z Phe-NHMe and Ac-(Aib-∆z Phe)3-NHMe,
the helical conformers with =±30°, ψ= ±60° for Aib residue and = ψ=
±30° for ∆z Phe are predicted to be most stable. The computational
studies for the positional preferences of ∆z Phe residue in the
peptide containing one ∆z Phe and nine Ala residues reveal the formation of a 310
helical structure in all the cases with terminal preferences for ∆zPhe.
The conformational behaviour of Ac-(∆z
Phe)n-NHMe with n≤4 is predicted to bc very labile. With
n> 4, degenerate conformational states with j, ψ values of 0° ± 90° adopt helical structures
which are stabilized by carbonyl-carbonyl interactions and the N-H-π interactions between the amino group of every ∆z Phe
residue with one C-C edge of its own phenyl ring. The results are in agreement
with the experimental finding that screw sense of helix for peptides containing
∆z Phe residues is ambiguous in solution. The helical structures
stabilized by hydrogen bond formation are found to be at least 3kCalmol-1
less stable. Conformational studies have also been carried out for the peptide
Ac-(∆E Phe)6,-NHMe and the peptide Ac-∆Ala- (∆z
Phe)6-NHMe containing ∆Ala residue at the N-terminal. The N-H -π interactions are absent in peptide Ac-(∆E Phe)6-NHMe.
|
| Page(s): | 417-425 |
| ISSN: | 0975-0959 (Online); 0301-1208 (Print) |
| Appears in Collections: | IJBB Vol.38(6) [December 2001] |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| IJBB 38(6) 417-425.pdf | 2.08 MB | Adobe PDF | View/Open |
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