Tobacco mosaic virus-enkephalin conjugates: potentiation of opioid activity.

Covalent tobacco mosaic virus-enkephalin analogue conjugates containing between 5 and 450 agonist molecules attached through their C-terminal amino acids were prepared and assayed in pharmacological and binding assays that distinguish between mu- and delta-receptors. Increases in peptide- and receptor-specific potency and affinity were observed with a certain preference of mu- over delta-receptors. The results may become important for mapping receptors or for isolating opiate receptor-bearing membrane vesicles.