Formation of Complexes between Protein Particles and Long Amphiphilic Polymers: Binding Isotherms versus Size and Surface of the Particles

Typical isotherms of protein binding here three serum albumins to hydrophobically modified polyacrylates (HMPA) were obtained by separation of free proteins from bound ones using capillary electrophoresis and the frontal analysis method. The main qualitative features of this association were anticooperativity, high sensitivity to the hydrophobicity of HMPAs, no sensitivity to the size of the proteins, and subtle differences related to small variations in primary structure. Keeping the structure of the protein surface unmodified, monomers and covalent dimers of the protein were compared. In terms of molar ratio, isotherms appeared to be not markedly dependent on the protein size. On the contrary, despite their similarity in terms of molecular weight, tertiary structure, surface, and binding to fatty acids, human and bovine serum albumins show marked differences in the composition of complexes. Short-range interactions, at the surface of the particles, dominate the association with long HMPA.