Interactions of hexachlorocyclohexanes with lipid bilayers

Quenching of the fluorescence of a hydrophobic analogue of tryptophan incorporated into lipid bilayers has been used to measure partition coefficients for lindane and the α- and δ-isomers of hexachlorocyclohexane. Partition coefficients between water and lipid are comparable to those between water and octanol and exhibit a negative temperature coefficient. Binding to the lipid phase is limited by saturation of the aqueous phase rather than of the lipid phase. The binding of lindane has no detectable effect on membrane fluidity as measured by fluorescence polarisation of diphenylhexatriene, or on the permeability properties of the membrane, as measured by the leak of carboxyfluorescein.