Dynamic characterization of phospholipid/protein competitive adsorption at the aqueous solution/chloroform interface

In the present paper, we use the drop volume method to study the dynamics of the competitive adsorption of the zwitterionic phospholipids (DPPC, DPPE, DMPC and DMPE) mixed with proteins (β-lactoglobulin, β-casein, and human serum albumin, respectively) at the chloroform/water interface. In order to investigate the main factors influencing the equilibrium interfacial tension of the mixed system (drops of lipid in chloroform formed in an aqueous protein solution environment), proteins of different conformation and concentration, and phospholipids of different structure have been investigated. It is observed that, with constant external protein concentration, the equilibrium interfacial tension γ decreases with the increase of internal lipid concentration. When the phospholipid concentration is close to the CAC, both the conformation and concentration of the protein do not influence the equilibrium interfacial tension of the mixed systems remarkably. With the same internal phase containing phospholipid in oil solvent and different external phases containing the protein in water, the γ–C isotherms show similar tendencies. Moreover, the structure of the phospholipid determines the equilibrium interfacial tension, where the lipid head group is much more significant rather than the chain length. The experimental results show that in DMPC-protein systems, the equilibrium interface tension decreases with the phospholipid concentration more rapidly than in DMPE-protein systems.