| Abstract
| - Transmembrane and in-plane oriented peptides have been prepared by solid-phase peptidesynthesis, labeled with 3,3,3-2H3-alanine and 15N-leucine at two selected sites, and reconstituted into orientedphophatidylcholine membranes. Thereafter, proton-decoupled 15N and 2H solid-state NMR spectroscopyat sample orientations of the membrane normal parallel to the magnetic field direction have been used tocharacterize the tilt and rotational pitch angle of these peptides in some detail. In a second step the sampleshave been tilted by 90°. In this setup the spectral line shapes are sensitive indicators of the rate of rotationaldiffusion. Whereas monomeric transmembrane peptides exhibit spectral averaging and well-definedresonances, larger complexes are characterized by broad spectral line shapes. In particular the deuteriumline shape is sensitive to association of a few transmembrane helices. In contrast, the formation of muchlarger complexes affects the 15N chemical shift spectrum. The spectra indicate that in liquid crystallinemembranes an amphipathic peptide of 14 amino acids exhibits fast rotational diffusion on both the 2H and15N time scales (>10-5 s). Extending the sequences to 26 amino acids results in pronounced changes ofthe 2H solid-state NMR spectrum, whereas the signal intensities of 15N solid-state NMR spectra degrade.Below the phase transition temperature of the phospholipid bilayers, motional averaging on the time scaleof the 2H solid-state NMR spectrum ceases for transmembrane and in-plane oriented peptides. Furthermoreat temperatures close to the phase transition the total signal intensities of the deuterium solid-state NMRspectra strongly decrease.
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