The transport of a charged adsorbate biomolecule in a porous polymeric adsorbent medium and its adsorption onto the covalently immobilized ligands have been modeled and investigated using molecular dynamics modeling and simulations as the third part of a novel fundamental methodology developed for studying ion-exchange chromatography based bioseparations. To overcome computational challenges, a novel simulation approach is devised where appropriate atomistic and coarse grain models are employed simultaneously and the transport of the adsorbate is characterized through a number of locations representative of the progress of the transport process. The adsorbate biomolecule for the system studied in this work changes shape, orientation, and lateral position in order to proceed toward the site where adsorption occurs and exhibits decreased mass transport coefficients as it approaches closer to the immobilized ligand. Furthermore, because the ligands are surrounded by counterions carrying the same type of charge as the adsorbate biomolecule, it takes the biomolecule repeated attempts to approach toward a ligand in order to displace the counterions in the proximity of the ligand and to finally become adsorbed. The formed adsorbate-ligand complex interacts with the counterions and polymeric molecules and is found to evolve slowly and continuously from one-site (monovalent) interaction to multisite (multivalent) interactions. Such a transition of the nature of adsorption reduces the overall adsorption capacity of the ligands in the adsorbent medium and results in a type of surface exclusion effect. Also, the adsorption of the biomolecule also presents certain volume exclusion effects by not only directly reducing the pore volume and the availability of the ligands in the adjacent regions, but also causing the polymeric molecules to change to more compact structures that could further shield certain ligands from being accessible to subsequent adsorbate molecules. These findings have significant practical implications to the design and construction of polymeric porous adsorbent media for effective bioseparations and to the synthesis and operation of processes employed in the separation of biomolecules. The modeling and analysis methods presented in this work could also be suitable for the study of biocatalysis where an enzyme is immobilized on the surface of the pores of a porous medium.


Chemical and Biochemical Engineering

Keywords and Phrases

Adsorbate Molecules; Adsorption Capacities; Bio Separation; Biocatalysis; Charged Ligands; Coarse Grain Model; Compact Structures; Computational Challenges; Counterions; Design and Construction; Immobilized Ligands; Ion-Exchange Chromatography; Ligand Complexes; Mass Transport Coefficients; Modeling and Analysis; Molecular Dynamics Modeling; Multi-Site; Polymeric Adsorbent; Polymeric Molecules; Pore Volume; Porous Adsorbent; Porous Medium; Simulation Approach; Transport Process; Volume Exclusion Effects; Adsorbates; Adsorption; Biomolecules; Chromatography; Complexation; Computer Simulation; Ion Exchange; Knowledge Based Systems; Molecular Dynamics; Molecules; Polymers; Porous Materials; Ligands; Argipressin[1 Deamino]; Immobilized Enzyme; Adsorption; Chemistry; Metabolism; Molecular Dynamics; Porosity; Surface Property; Transport at the Cellular Level; Biological Transport; Deamino Arginine Vasopressin; Enzymes, Immobilized; Molecular Dynamics Simulation; Solvents; Surface Properties; Water

International Standard Serial Number (ISSN)

0021-9606; 1089-7690

Document Type

Article - Journal

Document Version

Final Version

File Type





© 2010 American Institute of Physics (AIP), All rights reserved.

Publication Date

01 Aug 2010

PubMed ID