Influence of salts on protein interactions at interfaces of amphiphilic polymers and adsorbents

The protein-binding capacity of two different amphiphilic adsorbents was investigated to determine the effect of solvent additives on the binding of proteins in hydrophobic-interaction chromatography. There was no simple correlation between binding capacity and the lyotropic series such as those suggested by the two different theories proposed by Arakawa and Narhi and Melander and Horváth. Proteins are known to be dynamic flexible objects which continuously undergo changes in conformation and which may well be influenced by chaotropic salts. Are conformational changes of proteins at interfaces an important parameter involved in protein interactions with amphiphilic polymers and adsorbents? In an attempt to answer this question, the reactivity of the thiol group in human serum albumin (HSA) toward N-ethyl-3-(2-pyridyldisulfanyl)propionamide dextran was used as a model system to evaluate its correlation with the lyotropic series. The results indicate that the thiol-disulfide exchange reaction at interfaces of amphiphilic polymers is influenced by the type of salt used.