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Designing of peptides with left handed helical structure by incorporating the unusual amino acids

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Title Designing of peptides with left handed helical structure by incorporating the unusual amino acids
 
Creator Nandel, Fateh S
Malik, Nandita
Virdi, Manju
Singh, Balvinder
 
Description 195-203
The conformational behaviour of ∆Ala has
been investigated by quantum mechanical method PClLO in the model dipeptide Ac-∆Ala-NHMe and in the model tripeptides Ac-X-∆Ala-NHMe with X=Gly, Ala, Val, Leu, Abu and Phe and is found to
be quite different. The computational results suggest that in the model
tripeptides the most stable conformation corresponds to ϕ = -30°, Ψ1 = 120o and ϕ2= Ψ2 = 30° in which the >C=0
of the acetyl group is involved in hydrogen bond formation with N-H of the
amide group. Similar results were obtained for the conformational behaviour of D-Ala in Ac-D-Ala-NHMe and
Ac-Ala-D-Ala-NHMe.

The conformational behaviour of the amino
acids ∆Ala, D-Ala, Val and Aib in model tripeptides have been utilized in the
designing of left handed helical peptides. It is shown that the peptide
HCO-(Ala-D-Alak NHMe can adopt both left and right handed helix whereas in the
peptide Ac-(Ala-∆Ala)3-NHMe
the lowest energy conformer is b-bend ribbon structure. Left handed helical structure with ϕ=30°, Ψ=60o for D-Ala residues and ϕ= Ψ= 30° for ∆Ala is found to be more stable by 4 kcal mole-1 than the
corresponding right handed helical structure for the peptide Ac-(Val-∆Ala)3
NHMe. In both the peptides Ac-(Val-∆Ala)3,-NHMe and AC-(D-Val-∆Ala)3,-NHMe
the most stable conformer is the left handed helix . Comparisons of results for
Ac-(Ala-∆Ala)3 NHMe and Ac-(Val-∆Ala)3
NHMe and Ac-(D-Ala-∆Ala)3-NHMe and Ac-(D-Ala-∆Ala)3
-NHMe also re veal that the Val residues facilitate the population of 310
left handed helix over the other conformers. It is also shown that the  conformational behaviour of Aib residue
depends on the chirality of neighbouring amino acids, i.e. Ac-(Aib-Ala)3,-NHMe
adopts right handed helical structure whereas AC-(Aib-D-Ala)3,-NHMe is
found to be in left handed helical structure.
 
Date 2012-12-31T19:15:00Z
2012-12-31T19:15:00Z
1999-06
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/15435
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.36(3) [June 1999]