Monolayers of Human Plasma Fibronectin at the Air/Water Interface

Human plasma fibronectin forms spread monolayers at the air/solution interface. The properties of these monolayers have been examined as a function of the composition, pH, and temperature of the aqueous phase by using low-pressure surface manometry and surface potentials. From the isotherms the molecular weight of HPFN was determined as 4.5 × 10⁵ daltons, in agreement with the expected double-chain form of the protein. The surface densities at the highest pressures studied strongly indicate extensive folding. The second virial coefficients at 25 and 10 °C and the entropies of compression suggest several folding and packing patterns depending on the charge state of the glycoprotein.