EFFECT OF SOME POTASSIUM-SELECTIVE CROWN-ETHERS ON THE PERMEABILITY AND STRUCTURE OF A PHOSPHOLIPID MEMBRANE

The effect of some new crown ethers on the cation efflux and phase tra nsition parameters of dipalmitoyl phosphatidylcholine liposomes was st udied. The effects were correlated with the lipophilicity of the crown ethers. The results indicate that the presence of two crown ring stru ctures in one crown ether molecule is a prerequisite for the increase of ion permeability of liposomes. The effective crown ethers decrease the temperature, enthalpy and cooperativity of the gel-to-liquid cryst alline phase transition. The crown ethers increase membrane permeabili ty for potassium and, to a lesser extent, for rubidium and sodium. The ratio of permeability increase for potassium/rubidium significantly c orrelates with the lipophilicity of the crown ethers.