Interactions of Uranyl Ions with Lipid Bilayer Membranes

Uranyl ions (UO2(2+)), once bound to the phosphate moieties of phospholipid head groups, stabilize bimolecular lipid membranes (BLMs) as well as decrease the nonactin-induced membrane conductance. UO2(2+) bind to a phosphatidyl choline-cholesterol (2:1, molar ratio) BLM surface with a dissociation constant of 2.3 microM and a maximum change in surface potential of 88 mV, which corresponds approximately to one uranyl ion per 31 nm2 surface area. Furthermore, uranyl ions can penetrate the lipid bilayers as neutral complexes such as uranyl acetate.