SPECTROSCOPIC STUDIES OF THE INTERACTIONS OF THE PYRETHROID INSECTICIDE FENVALERATE WITH GRAMICIDIN

Fenvalerate is a pyrethroid insecticide which interacts with ionic cha nnels. Using circular dichroism technique we have studied the interact ion of fenvalerate with gramicidin, a model channel peptide which tran sports ions. In most organic solvents, gramicidin exists as a double h elix except in trifluoroethanol where it exists as a channel forming s ingle stranded beta(6.3) helical monomer. In model lipid membranes, un der certain experimental conditions, gramicidin exists as a channel fo rming single stranded beta(6.3) helical dimer. Our results show that f envalerate interacts more with the single stranded beta(6.3) helical m onomer or dimer than with the double helical form of gramicidin. This was further confirmed by an increase in the rate of gramicidin mediate d proton transport in liposomes by fenvalerate, using the pH sensitive fluorophore, pyranine.