title: Gibbs free energy of adsorption for biomolecules in ion-exchange systems.
abstract: The Gibbs free energy of adsorption (delta G0ads) was estimated for several amino acids, peptides and proteins in a cation-exchange system. Using the steric mass action formalism that describes biomolecular adsorption in ion-exchange systems, the delta G0ads was chromatographically determined under infinitely dilute conditions. The delta G0ads measured for seven globular proteins ranged from -5.7 to -13.9 kcal/mol. The average bond energy (defined as delta G0ads divided by the number of bonds formed between the protein and the surface) for these proteins varied from -1.1 to -1.7 kcal/mol. These bond energies were found to be comparable to the bond energies for lysine and arginine (-1.1 and -1.5 kcal/mol, respectively), the amino acids which primarily contribute to the cation-exchange of proteins. In contrast, an elevated average bond energy of -2.6 kcal/mol was observed for two peptides and protamine (a polypeptide) suggesting that synergistic binding may play a role for unstructured macromolecules, but not for globular proteins.
authors.affiliation: Isermann Department of Chemical Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180.
authors.forename: J A
authors.initials: JA
authors.lastname: Gerstner
authors.forename: J A
authors.initials: JA
authors.lastname: Bell
authors.forename: S M
authors.initials: SM
authors.lastname: Cramer
mesh_terms: D000042:Absorption; D000596:Amino Acids / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D002852:Chromatography, Ion Exchange; D011506:Proteins / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D011506:Proteins