(364a) Examining the Effect of Protein Size on Transport and Adsorption in Polymer-Modified Ion-Exchange Media

The effect of protein size on the balance between protein transport and adsorption that accounts for observed column breakthrough performance is explored. The model proteins lysozyme, lactoferrin, and a monoclonal antibody were studied on the traditional resin SP Sepharose^TM FF and the dextran-modified resins SP Sepharose XL and Capto^TM S. Adsorption isotherms show modest increases in static binding capacity for dextran-modified materials, reflecting a larger available binding volume. Protein uptake visualized by confocal microscopy reveals significant changes with protein size and also reflects consistently faster uptake in the dextran-modified resins, which can be understood in terms of the comparative ability of adsorbed protein to move in the pore space. The faster transport in XL and Capto shifts the optimum operation to lower ionic strengths where static capacities are higher, resulting in greatly improved dynamic binding capacities. Further qualitative insights into column performance are gained through consideration of protein and resin properties.