Fluorescence spectroscopy studies of the effects of pyrethroids on the DPPC vesicles

The interactions of pyrethroids with membrane lipids have been studied by means of fluorescent membrane probe DPH. Pyrethroids located in the interior hydrophobic regions of the lipid bilayer, differed in their effectiveness of lowering the phase transition temperature and in their ability to broaden the temperature range of this transition. With the increase in the concentrations of pyrethroids, the effects of disordering hydrocarbon packing were increased by pyrethroids. Fluorescence polarizations (P) were decreased in gel state, but not changed in fluid state by permethrin. The pyrethroids containing a cyano substituent could not only disturb the hydrocarbon packing in the bilayer core, but also cause collisional quenching of DPH fluorescence in gel state, P were decreased, then were increased and at last were decreased slightly again as the concentrations were increased, in fluid state P were not changed substantially at low concentrations and were increased obviously when the concentrations were higher.