<> "The repository administrator has not yet configured an RDF license."^^ . <> . . . "Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide."^^ . "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."^^ . "2000-07-05" . . "273" . "2" . . "Elsevier Science"^^ . . . "Biochemical and biophysical research communications"^^ . . . "0006291X" . . . . . . . . . . . . . "Raghuvansh"^^ . "Kishore"^^ . "Raghuvansh Kishore"^^ . . "A"^^ . "Kumar Thakur"^^ . "A Kumar Thakur"^^ . . "P"^^ . "Venugopalan"^^ . "P Venugopalan"^^ . . . . . . "Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (PDF)"^^ . . . . . "Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Image (PNG))"^^ . . . . . . "Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Image (PNG))"^^ . . . . . . "Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Image (PNG))"^^ . . . . . . "Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Image (PNG))"^^ . . . . . . "Collateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide. (Indexer Terms)"^^ . . . . . "HTML Summary of #315 \n\nCollateral existence of folded and extended conformations of the beta-Ala moiety in a model peptide.\n\n" . "text/html" . . . "QD Chemistry"@en . .