Study of hydrophobic interaction adsorption of bovine serum albumin under overloaded conditions using flow microcalorimetry

The adsorption behavior of bovine serum albumin (BSA) on a Sepharose based hydrophobic interaction support has been studied. Flow microcalorimetry has been used to determine the heat of adsorption under overloaded chromatogra phic conditions. These data have been complemented with capacity factor and isotherm measurements to provide insight on the mechanisms of adsorption. The heat of adsorption data have confirmed that the hydrophobic interaction adsorption of BSA under linear isotherm conditions is driven by entropy ch anges. Under overloaded (non-linear) conditions, however, it has been shown that the changes in enthalpy can drive adsorption; this behavior is not ev ident from analyses of capacity factor data, It is postulated that for BSA adsorption on the Sepharose derivative of interest, attractive force intera ctions between adsorbed protein molecules drive the adsorption process unde r overloaded conditions in a high (NH4)(2)SO4 environment, It is further po stulated that these interactions are due to a change in confirmation of the adsorbed protein under these conditions. (C) 1999 Elsevier Science B.V. Al l rights reserved.