Adsorption of charged macromolecules on mixed fluid membranes

The adsorption of charge rigid macromolecules, such as proteins from solution, on mixed (charged and neutral) lipid membranes is affected by several important factors. First, the mobile lipids in the membrane may rearrange, and demix locally to match the charge density of the apposed macromolecule, thus lowering the adsorption free energy. On the other hand, the (electrostatic) interaction between adsorbed macromolecules tends to lower the saturation coverage of the membrane. Additional factors, such as non-ideal lipid demixing or an elastic membrane response, enhanced by the presence of the charged macromolecules, may be at the base of the experimentally observed formation of high density protein domains and lateral macro-phase separation in lipid membranes.