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Conformational study of peptides containing dehydrophenylalanine Helical structures without hydrogen bond

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Title Conformational study of peptides containing dehydrophenylalanine Helical structures without hydrogen bond
 
Creator Nandel, Fateh S
Kaur, Harpreet
Malik, Nandita
Shankar, Neelaabh
Jain, Dharam V S
 
Description 417-425
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.
 
Date 2012-12-25T19:30:34Z
2012-12-25T19:30:34Z
2001-12
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/15329
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.38(6) [December 2001]