A photoaffinity-labelled insect sex pheromone for the moth Antheraea polyphemus

Abstract

SINCE the isolation of the first insect sex pheromone, bombykol, from the female silkmoth Bombyx mori¹ and its full identification by synthesis as (10E, 12Z)-10,12-hexadecadienol^2,3, the number of characterised pheromones has increased dramatically^4–7. The basic question of pheromone–receptor interactions remain unanswered, however. To devise a method which could be used to study such problems, it was necessary to modify the natural pheromone in such a way as to specifically label the binding site of its chemoreceptor cell. We chose to convert the acetate group, a common feature in Lepidoteran pheromones^4–7, into a diazoacetate derivative. Information about the active site of the pheromone receptor cell can then be obtained by reacting it irreversibly with a carbene derived from the diazoacetate group. In this procedure, the modified pheromone is radioactively labelled, and since the carbene is generated photolytically, the process is called photoaffinity labelling^8,9. We have used electrophysiological techniques as a very sensitive and rapid bioassay method to check the activity of the modified pheromone. We recorded the responses from single receptor cells and evaluated the changes in receptor potential and nerve impulses activity accompanying exposure of the antennae to a stream of pheromone^10–12. We describe here experiments showing that the diazoacetyl derivative of the pheromone acetate (VII) meets the requirements of a photoaffinity label for the study of the receptor.