Characterization of modified staphylococcal protein A containing phospholipid monolayer on both solution and slide...

A method is described for incorporation of water-soluble protein Staphylococcal protein A (SpA) into phospholipid monolayer using covalent protein-lipid conjugates in detergent solution. The amphiphilic conjugates have solubility properties very similar to intergral membrane proteins. When the conjugates are applied into dipalmitoyl-phosphatidic acid monolayer, a protein containing monolayer is formed on subphase surface. The monolayer is transferred to pre-coated substrate surface to form an artificial membrane. Results show that unmodified SpA is readily ejected from the monolayer when compressing the monolayer but modified SpA incorporates into the monolayer stably. The incorporation of the protein is proportional to the lipid coupling degree. When the protein is excessively modified, the IgG binding activity of the SpA in the membrane is lost significantly.