| Abstract
| - Knowledge of the alignment of α-helical polypeptides with respect to the membrane surfaceand their dynamics in the membrane are key to understanding the functional mechanisms of channels,antibiotics, and signal or translocation peptides. In this paper polypeptides have been labeled with [3,3,3-2H3]alanine as well as with 15N at single site amide positions and reconstituted into oriented phospholipidbilayers. A transmembrane and two amphipathic helical polypeptides with the deuterium label at orthogonalpositions have been investigated by deuterium and proton-decoupled 15N solid-state NMR spectroscopy.The 15N chemical shift measurements and the deuterium quadrupole splitting exhibit a highly complementaryfunctional dependence with respect to the spatial alignment of the polypeptide. Therefore, the combinationof these two measurements allows one to determine both the tilt and the rotational pitch angle with highprecision. In addition, the deuterium line shape is very sensitive to mosaic spread and the relative orientationof the peptide. The solid-state NMR measurements indicate that the model sequences exhibit a smalldegree of mosaicity, when at the same time the phospholipid headgroup region is significantly distorted.Furthermore, the 2H solid-state NMR spectra reveal small orientational and dynamic differences whenthe fatty acyl chain composition of the phosphatidylcholine bilayers is modified.
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