Fluorine NMR spectroscopy has been used to identify and quantitate metabolites of profluralin appearing in the urine of rats postingestion of the herbicide. The chemical shift of the trifluoromethyl group was shown to be a useful indicator of the chemical type of metabolite, and the shifts for the classes of materials previously identified as metabolites have been determined. By use of chemical shift criteria this work provides evidence for several metabolites that have not been recognized in previous work; some of these remain incompletely characterized. Though the number and types of metabolites detected in the urine were consistent from animal to animal, the time course for appearance of metabolites was found to be animal dependent.

The C-terminal "address" sequences of prodynorphin-derived opioid peptides contain an unusually high proportion of basic residues, which are known to be crucial for conferring high activity and selectivity for kappa-opioid receptors. In an effort to investigate the possibility that the polycationic "tails" may be involved in a coulombic interaction with a complementary polyanionic receptor domain, we attached a series of achiral peptide-like cationic fragments to the C-terminus of the opioid peptide "message", Tyr-Gly-Gly-Phe. Binding of the various compounds to opioid receptor types in guinea pig brain membranes was weak, and the pharmacologic activities in the guinea pig ileum were marginal. These results indicate either that the chosen ligand design does not satisfy the structural requirements of the hypothesized coulombic interaction or that the latter is a minor criterion governing receptor recognition.