Effect of salts and temperature on the adsorption of bovine serum albumin on polypropylene glycol-Sepharose under linear and overloaded chromatographic conditions.

The interaction thermodynamics associated with bovine serum albumin (BSA) adsorption on polypropylene glycol (PPG)-Sepharose CL-6B gel, using ammonium and sodium sulfate was studied. Analysis of data under linear conditions was accomplished with the stoichiometric displacement retention model and preferential interaction approach. Preferential interaction analysis indicated a strong entropic driving force due to the release of a large amount of solvent on adsorption. Flow microcalorimetry provided direct heat of adsorption measurements under overloaded conditions and confirmed that the adsorption of BSA on PPG-Sepharose was entropically driven within the range of conditions studied. Using these data in combination with isotherm measurements, it is shown that protein surface coverage, salt concentration, salt type and temperature affect the enthalpic and entropic behavior in hydrophobic interaction chromatography (HIC). This study shows that protein-sorbent interactions can be strongly influenced by the degree of water release, protein-protein interactions on the surface, and the re-orientation and/or reconfiguration of the adsorbed protein.