PHASE-EQUILIBRIA FOR AQUEOUS PROTEIN-POLYELECTROLYTE GEL SYSTEMS

A molecular-thermodynamic analysis is directed toward predicting the p artitioning of aqueous proteins into charged hydrogels. This analysis takes into account size exclusion by the network, electrostatic intera ctions, and the osmotic-pressure difference between a hydrogel and its surrounding solution. Electrostatic interactions in the polyelectroly te gel can be described by Debye-Huckel theory, or the Mean Spherical Approximation, or Katchalsky's cell model for polyelectrolyte solution s. The cell model gives best agreement with experimental partition coe fficients for cytochrome c. The quasi-electrostatic potential differen ce between a gel and its surrounding solution demonstrates how the ele ctrostatic contribution to the protein partition coefficient depends o n protein charge, gel-charge density, and solution ionic strength. Fin ally, a qualitative guide is presented for design of a polyelectrolyte gel such that it exhibits specified swelling and partitioning propert ies.