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Molecular reorientation processes in crystalline thiophene and furan have been studied using pulse nmr techniques, over a range of temperature. The results obtained have been evaluated in the context of literature data on the heat capacities and crystal structures of these systems; this evaluation has been facilitated by the use of potential energy calculations for a molecule in the crystal lattice, based upon the empirical atom–atom approximation for the intermolecular interactions. In the case of furan, all available data can be reconciled in a self-consistent picture of the dynamic structure of the crystal. In the case of thiophene, however, various inconsistencies suggest that the published crystal structure determination should be repeated, and that further work on the pulse nmr at lower temperatures is necessary.

The causative agent of toxicity in cultured mussels from a localized area of eastern Prince Edward Island has been identified as domoic acid, a neuroexcitatory amino acid. The toxin was isolated by a number of different bioassay-directed separation techniques including high-performance liquid chromatography, high-voltage paper electrophoresis, and ion-exchange chromatography, and characterized by a number of spectroscopic techniques including ultraviolet, infrared, mass spectrometry, and nuclear magnetic resonance. The isolation and purification methods are described in detail and some new analytical data for domoic acid are reported. Keywords: shellfish toxin, domoic acid, neurotoxin, bioassay-directed analysis.