Mixed-mode chromatography is a new technology for the purification of immunoglobulin (IgG). Previous researches indicated that a certain concentration of sodium caprylate (NaCA) could significantly reduce the adsorption of serum albumins and improve the efficiency of mixed-mode chromatography. With MEP HyperCel resin and bovine serum albumin (BSA) as the model

the interactions between NaCA and BSA were investigated by static adsorption and isothermal titration calorimetry (ITC) in the present work. The influences of concentration of NaCA

pH

salt addition and temperature were discussed. The static adsorption experiments showed that the adsorption capacities of BSA and IgG firstly decreased and then increased with increasing NaCA concentration. The influence of NaCA on BSA was much obvious than IgG. ITC analysis indicated that the interactions between NaCA and BSA were quite stronger than those for IgG

and the hydrophobic force dominated the NaCA-BSA interactions. With NaCA addition

the adsorption of BSA decreased with increasing pH value or temperature

and different salts showed varying impacts. ITC analysis also demonstrated that the NaCA-BSA interactions were influenced by pH

salt addition and temperature. In general

ITC results were consistent with those of adsorption experiments

which demonstrated that ITC could be used to evaluate the interactions between small molecule and protein

then study the mechanism of specific additive on protein adsorption.