Interactions of 2,2,2-trifluoroethanol with melittin

Melittin dissolved in 42% trifluoroethanol‐water at pH 2 has been shown to be α‐helical between residues 6 and 12 and between residues 13 and 25, with the two helical regions separated by a bend at the Leu13 residue. The inter‐helix angle was found to be 154 ± 3° at 0 °C and 135 ± 3° at 25 °C. The d...

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Veröffentlicht in:Magnetic resonance in chemistry 2009-11, Vol.47 (11), p.925-931
Hauptverfasser: Neuman Jr, Robert C., Gerig, John T.
Format: Artikel
Sprache:eng
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Zusammenfassung:Melittin dissolved in 42% trifluoroethanol‐water at pH 2 has been shown to be α‐helical between residues 6 and 12 and between residues 13 and 25, with the two helical regions separated by a bend at the Leu13 residue. The inter‐helix angle was found to be 154 ± 3° at 0 °C and 135 ± 3° at 25 °C. The dominant conformation of the peptide is thus similar to those observed by previous workers for the peptide in a variety of media. At 25 °C, intermolecular nuclear Overhauser effects arising from nuclear spin dipole‐dipole interactions between melittin hydrogens and fluorines of the solvent are essentially those expected for a system that is homogeneous as regards concentration and translational diffusion of the peptide and fluoroalcohol components. However, at 0 °C, peptide‐trifluoroethanol cross‐relaxation terms are negative, a result consistent with the conclusion that fluoroalcohol molecules associate with the peptide for times (∼1 ns) that are long compared to the time of a typical peptide‐fluoroalcohol diffusive encounter (∼0.2 ns). Such interactions may be responsible for the reduction of the translational diffusion coefficient of trifluoroethanol produced by dissolved peptides. Copyright © 2009 John Wiley & Sons, Ltd. Melittin in 42% trifluoroethanol–water at pH 2 is shown to have two helical regions separated by a bend at Leu13. At 25 °C, solvent fluorine–peptide hydrogen spin dipolar interactions are those expected for a system that is homogeneous as regards concentration and diffusion of the components. At 0 °C, peptide–trifluoroethanol cross‐relaxation terms are negative, a result consistent with interaction of fluoroalcohol molecules with the peptide for times that are long compared to the time of a peptide–alcohol diffusive encounter.
ISSN:0749-1581
1097-458X
DOI:10.1002/mrc.2489