Protein-protein resistance investigated by quartz crystal microbalance.

By use of quartz crystal microbalance with dissipation (QCM-D), we have investigated the adsorption of proteins such as fibrinogen, bovine serum albumin or lysozyme on the surface of soy protein film in PBS buffer solution in real time. Our studies demonstrate that the proteins can be adsorbed on soy protein film at a pH between the isoelectric point (pI(sp)) of soy protein film and that (pI(fp)) of the foreign protein, where the adsorption decreases with the concentration of added salt. Beyond the pH range, soy protein generally resists the adsorption of the foreign protein due to electrostatic repulsion, which is slightly affected by the concentration of the added salt in the range we investigated. At a pH close to pI(sp) or pI(fp), the proteins can also be adsorbed on soy protein film due to hydrophobic interactions. The present study reveals that the protein resistance of soy protein film is determined by electrostatic interactions, hydrophobic interactions and hydrogen bonding between the foreign protein and soy protein.