Dataset Information

Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols.

ABSTRACT: Four diastereoisomers of 2-fluorobicyclo[2.2.1]heptan-7-ols were computationally investigated by using quantum-chemical calculations, and their relative energies were analyzed on the basis of stereoelectronic interactions, particularly the presence or otherwise of the F???HO intramolecular hydrogen bond in the syn-exo isomer. It was found through NBO and AIM analyses that such an interaction contributes to structural stabilization and that the (1h)J(F,H(O)) coupling constant in the syn-exo isomer is modulated by the n(F)??*(OH) interaction, i.e., the quantum nature of the F???HO hydrogen bond.

SUBMITTER: de Rezende FM

PROVIDER: S-EPMC3458742 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols.

de Rezende Fátima M P FM Moreira Marilua A MA Cormanich Rodrigo A RA Freitas Matheus P MP

Beilstein journal of organic chemistry 20120802

Four diastereoisomers of 2-fluorobicyclo[2.2.1]heptan-7-ols were computationally investigated by using quantum-chemical calculations, and their relative energies were analyzed on the basis of stereoelectronic interactions, particularly the presence or otherwise of the F∙∙∙HO intramolecular hydrogen bond in the syn-exo isomer. It was found through NBO and AIM analyses that such an interaction contributes to structural stabilization and that the (1h)J(F,H(O)) coupling constant in the syn-exo isome ...[more]

PMID: 23019452

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Project description:Previous work shows that the transiently populated, on-pathway intermediate in Im7 folding contains three of the four native alpha-helices docked around a core stabilised by native and non-native interactions. To determine the structure and dynamic properties of this species in more detail, we have used protein engineering to trap the intermediate at equilibrium and analysed the resulting proteins using NMR spectroscopy and small angle X-ray scattering. Four variants were created. In L53AI54A, two hydrophobic residues within helix III are truncated, preventing helix III from docking stably onto the developing hydrophobic core. In two other variants, the six residues encompassing the native helix III were replaced with three (H3G3) or six (H3G6) glycine residues. In the fourth variant, YY, two native tyrosine residues (Tyr55 and Tyr56) were re-introduced into H3G6 to examine their role in determining the properties of the intermediate ensemble. All four variants show variable peak intensities and broad peak widths, consistent with these proteins being conformationally dynamic. Chemical shift analyses demonstrated that L53AI54A and YY contain native-like secondary structure in helices I and IV, while helix II is partly formed and helix III is absent. Lack of NOEs and rapid NH exchange for L53AI54A, combined with detailed analysis of the backbone dynamics, indicated that the hydrophobic core of this variant is not uniquely structured, but fluctuates on the NMR timescale. The results demonstrate that though much of the native-like secondary structure of Im7 is present in the variants, their hydrophobic cores remain relatively fluid. The comparison of H3G3/H3G6 and L53AI54A/YY suggests that Tyr55 and/or Tyr56 interact with the three-helix core, leading other residues in this region of the protein to dock with the core as folding progresses. In this respect, the three-helix bundle acts as a template for formation of helix III and the creation of the native fold.

Dataset Information

Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols.

Publications

Conformational analysis, stereoelectronic interactions and NMR properties of 2-fluorobicyclo[2.2.1]heptan-7-ols.

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