(517b) Biomolecular Transport and Adsorption in Porous Polymer Adsorbent Media

Ion-exchange chromatography (IEC) employing porous adsorbent media in which the affinity group/ligand is linked to the base matrix via a polymeric extender, plays a significant role in the downstream separation of biomolecules. In order to achieve a more complete understanding, a multi-stage approach and the molecular dynamics (MD) modeling and simulation technique have been used. In stage I, the structures of the porous polymeric extender layers are constructed and characterized in atomistic details. In stage II, the responses of the porous extender layers from Stage I to the immobilization of charged ligands and the effects of the porous structures on the ligand distribution and electroneutrality are studied. Non-uniform ligand density distributions and local electroneutrality are found to exist in these adsorbent media under practical operational conditions and they depend significantly on the surface density of polymeric extender. In stage III, the transport and adsorption of a charged adsorbate biomolecule (desmopressin) from the bulk solution and in the porous polymeric layers are investigated. Specifically, the conformation, effective mass transport coefficient, interaction potential energy of the biomolecule at different locations, and the evolution of the porous structure, distributions of counterions and immobilized ligands, and the resultant electrical filed during biomolecular adsorption are studied. The results from these studies not only uncover important fundamental aspects of IEC-based bioseparations that have traditionally been overlooked, but also have very significant implications in the design and construction of the porous polymer adsorbent media and in the macroscale modeling of the system wide dynamics.