Perturbation of artificial and biological membranes by organic compounds of aliphatic, alicyclic and aromatic structure.

Aliphatic, alicyclic and aromatic hydrocarbons interact with biological membranes. Until now little has been known about their mode of interaction with the membrane bilayer and membrane integral proteins with toxic effects to cells. The lipid theory hypothesis explains the toxic effects by the organic solvent-induced disorder in the lipid bilayer, which indirectly affects the function of membrane-embedded proteins. The extent of bilayer perturbations is ascribed to the solvent accumulation in the bilayer, which is related only to the lipophilicity of the molecule, independent of the chemical structure. In this study the fluidizing effects of aliphatic, alicyclic and aromatic hydrocarbons were compared. Membrane fluidity changes were estimated from the pyrene excimer formation, using pyrene and pyrene derivatives to label specifically the localization of solvent molecules in the transverse plane of the bilayer. Liposomal, microsomal and synaptosomal membrane preparations were evaluated because proteins and cholesterol, as natural membrane components, increase the bilayer order and reduce the organic solvent membrane/buffer partition. In the concentration range investigated, only the aromatic solvents disorder the lipid bilayer, with the greatest perturbation in the centre of the bilayer. These results are related to structural properties of the organic solvents investigated.