Gibbs free energy of adsorption for biomolecules in ion-exchange systems

doi:10.1016/0301-4622(94)00006-9

Biophysical Chemistry

Volume 52, Issue 2, October 1994, Pages 97-106

https://doi.org/10.1016/0301-4622(94)00006-9 Get rights and content

Abstract

The Gibbs free energy of adsorption (ΔG_ads⁰) 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 ΔG_ads⁰ was chromatographically determined under infinitely dilute conditions. The ΔG_ads⁰ measured for seven globular proteins ranged from −5.7 to −13.9 kcal/mol. The average bond energy (defined as ΔG_ads⁰ 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.

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