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primary topic: Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide.

Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide.
type: AcademicArticle
type: Article
abstract: The single-crystal X-ray diffraction analysis of a nonchiral beta-Ala-containing model peptide, Boc-beta-Ala-Aib-OCH(3) 1 (beta-Ala, 3-aminopropionic acid; Aib, alpha-aminoisobutyric acid), establishes the coexistence of distinctly different backbone conformations in two crystallographically independent molecules, A and B, in the asymmetric unit. Interestingly, the central mu torsion angle around the -C(beta)-C(alpha)- bond of the conformationally flexible beta-Ala residue appears to be critical in dictating the overall distinct structural features, i.e., in molecule A it adopts a folded gauche conformation: mu = -71.0 degrees, whereas it favors an extended trans conformation, mu = 161.2 degrees, in molecule B. As expected, the stereochemically constrained Aib residue preferred an energetically favorable folded backbone conformation, the torsion angles being phi = 46.2 degrees and psi = 48.3 degrees for molecule A and phi = -43.6 degrees and psi = -45.5 degrees for molecule B, lying in the left-handed and right-handed helical regions of the Ramachandran map, respectively. Considering the signs as well as the magnitudes of the backbone torsional angles, molecule A typically folds into a pseudo type III' beta-turn-like structure while molecule B prefers an overall extended conformation. Entrapping the two dramatically distinct conformational characteristics in the crystalline state clearly suggests that the gauche and the trans effects of the beta-Ala moieties are indeed energetically accessible to a short linear peptide and receive strong experimental support. The analyses permitted us to emphasize that in addition to conformational constraints of the neighboring residue, the chemical nature of the side-chain acyclic substituents and the "local environments" collectively seem to influence the stabilization of the folding-unfolding behavior of the two methylene units (-CONH-CH(2)-CH(2)-CONH-) in 1.
date: 2000-07-05
volume: 273
issue: 2
is part of: Biochemical and biophysical research communications
status: peerReviewed
status: published
author list: authors
type: EPrint
type: ArticleEPrint
is part of: repository
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subject: QD Chemistry

Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (PDF)
type: Document

Elsevier Science
type: Organization

Biochemical and biophysical research communications
type: Collection
issn: 0006291X

Raghuvansh Kishore
type: Person
given name: Raghuvansh
family name: Kishore

A Kumar Thakur
type: Person
given name: A
family name: Kumar Thakur

P Venugopalan
type: Person
given name: P
family name: Venugopalan

Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Image (PNG))
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Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Image (PNG))
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Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Image (PNG))
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Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Image (PNG))
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Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Indexer Terms)
type: Document
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primary topic: Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide.

QD Chemistry
type: Concept