Lipid membranes loaded with Ca2+ and Zn2+ cations

We have studied the interactions of calcium and zinc with the biomimetic membrane made of dipalmitoyl-phosphatidylcholine (DPPC). The small angle neutron experiment on oriented multilamellar samples showed clearly differences in the effects of the two cations. For both, a bilayer thickness increases due to divalent metal ion (Me2+) binding, reaching the maximum at stoichiometry Me2+:DPPC∼1:7 mol/mol. However, while the further increase in Ca2+ results in a bilayer thinning down to the level of pure DPPC, the Zn2+ binding indicates the behaviour of a typical isotherm, reaching a level of saturation.