Previous work by several groups has shown that the combination of spin--spin coupling constants and spectral density components (derived from spin--lattice relaxation and/or nuclear Overhauser measurements) may aid in the task of conformational determination of peptides in solution. Using the peptide formyl-L-methionyl-L-leucyl-L-phenylalanine, which is a potent specific chemotactic agent for leucocytes, we show the following: (a) that 3JNHCH coupling constants are consistent with a high degree of rigidity in the peptide backbone in solution, (b) that 3H isotopic substitution in combination with relaxation data taken at different Larmor frequencies enables spectral density, and thence conformational, information to be obtained, (c) that side-chain conformations for this molecule mirror, in some aspects, those found in the solid state for other peptides containing the same residues, and (d) that temperature dependence of amide chemical shifts does not have direct implication concerning the existence of intramolecular hydrogen bonds in peptides. We are able to propose a family of conformations which appear to interchange rapidly on the NMR time scale and are characterized by a distribution of side-chain rotamers. The basic backbone conformation is, or closely approximates, a small beta antiparallel pleated sheet and as such suggests a possible mode of receptor--chemotactic peptide interaction.

Measurements of spin-lattice relaxation in nematic and smectic liquid crystals are contrasted to recent theoretical predictions for T^ in these phases.

The deuteron fast Fourier transform (FFT) spectra of the ring deuterated nematogens para-azoxyanisole (PAA-d8) and p-methoxybenzylidene p-n-butylaniline (MBBA-d8) have been studied as a function of temperature. An interpretation of the spectra is presented. It is based on the assumption of nonequivalent deuterons, a twist angle φ between the planes of the benzene rings, and an asymmetry order parameter δ in addition to the usual nematic order parameter S. The temperature dependences of δ and φ have been obtained.

1 H/ 13 C/ 119 Sn triple-resonance 3D-NMR spectroscopy is used to characterize the tin-containing structures in the organotin polymer n-Bu3SnPBD (PBD ) polybutadiene). Triple-resonance techniques, when used together with pulsed field gradient coherence selection, permit selective detection of the structure fragments near 119 Sn atom while removing intense signals of the PBD backbone from the spectrum. Three frequency dimensions provide enormous spectral dispersion, permitting the resolution of many signals that are not observable in 1D-NMR spectra. The simultaneous correlation of resonances from three nuclei provides a large amount of unambiguous atomic connectivity information. The capabilities of modern instruments are such that it is possible to perform these experiments without the benefit of isotopic labeling, despite the low concentration of chain ends and the low occurrence of fragments with 1 H, 13 C, and 119 Sn isotopes.

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