Surface rheology and adsorption kinetics reveal the relative amphiphilicity, interfacial activity, and stability of human exchangeable apolipoproteins.

Exchangeable apolipoproteins are located in the surface of lipoprotein particles and regulate lipid metabolism through direct protein-protein and protein-lipid interactions. These proteins are characterized by the presence of tandem repeats of amphiphatic alpha-helix segments and a high surface activity in monolayers and lipoprotein surfaces. A noteworthy aspect in the description of the function of exchangeable apolipoproteins is the requirement of a quantitative account of the relation between their physicochemical and structural characteristics and changes in the mesoscopic system parameters such as the maximum surface pressure and relative stability at interfaces. To comply with this demand, we set out to establish the relations among alpha-helix amphiphilicity, surface concentration, and surface rheology of apolipoproteins ApoA-I, ApoA-II, ApoC-I, ApoC-II, and ApoC-III adsorbed at the air-water interface. Our studies render further insights into the interfacial properties of exchangeable apolipoproteins, including the kinetics of their adsorption and the physical properties of the interfacial layer.