The magnitudes and orientations of the principal elements of the 15N chemical shift and 1H−15N dipolar coupling interaction tensors pertaining to the glycine residue in 15 N-acetyl glycine (NAG) and [15N-Gly]collagen were determined by the analysis of one-dimensional dipolar chemical shift powder patterns. A one-dimensional 1H−15N dipolar 15N chemical shift spectrum was obtained on a [15N-Gly]collagen fiber sample with the fiber axis oriented parallel to the external magnetic field. The dipolar chemical shift spectrum enabled the orientation of the peptide plane to be determined relative to the direction of the applied magnetic field or the triple-helix axis of the collagen fiber. The magnitudes of the principal elements of the tensors and their orientations in the molecular frame for these two sites are quite different. The magnitudes of the chemical shift tensors are 42.3, 67, and 223.4 ppm for [15N-Gly]collagen and 37, 82.8, and 220.4 ppm for NAG. The angle (βN) between the least shielded 15N chemical shift tensor element, σ33N, and the N−H bond is 24.5° for [15N-Gly]collagen and 25.5° (or 154.5°) for NAG. The angle (αN) between the most shielded 15N chemical shift tensor element, σ11N, and the projection of the N−H bond on the σ11N−σ22N plane is 145° for [15N-Gly]collagen and 25° (or 155°, 205°, or 335°) for NAG. Because of the identical dipolar chemical shift powder patterns for four different αN values (35°, 145°, 215°, and 325°) the correct value of the αN angle was determined as 145° using the dipolar chemical shift spectrum of the oriented [15N-Gly]collagen sample.

The synthesis and characterization of novel thermotropic liquid crystals based on thiophene are reported. In these molecules, a thiophene ring, 1−4 disubstituted phenyl rings, and ester and azomethine linking units form the core fragment, and an alkoxy unit serves as the terminal group. All compounds exhibited an enantiotropic nematic phase, as confirmed by hot-stage polarizing microscope analysis and differential scanning calorimetry. Isotropic 13C chemical shift values measured from CPMAS experiments on crystalline solid and nematic phases were compared to the values obtained from the static nematic phase. These experiments demonstrate the alignment of molecules in the magnetic field. Lower melting and clearing values are observed when two phenyl rings are part of the mesogen, while the addition of a third phenyl ring increases these values.

A simple one-dimensional dipolar shift solid-state NMR experiment is demonstrated to study the backbone conformation of membrane-associated peptides embedded in phospholipid bilayers. The nitrogen-15 chemical shift and 1 H-15 N dipolar coupling parameters are measured on a magainin peptide selectively labeled with a 15 N isotope at the Gly-18 site. Fully hydrated multilamellar vesicles and uniaxially oriented bilayer samples are used to determine the orientation of the peptide plane relative to the direction of the external magnetic field. It is inferred that the 1 H-15 N dipolar coupling 15 N chemical shift doublet of the [ 15 N-Gly-18]magainin peptide oriented in lipid bilayers is asymmetrical. Calculation of the experimental dipolar shift spectrum suggests that the shape of the asymmetrical doublet is highly sensitive to the orientation of the principal axes of the 15 N chemical shift tensors in the molecular frame as well as the backbone conformation of the peptide embedded in lipid bilayers.