Hydrophobic interaction chromatography on uncharged Sepharose derivatives. Effects of neutral salts on the adsorption of proteins.

In the presence of different neutral salts in high concentrations (ionic strength 1-3 M), pentyl-Sepharose was saturated with human serum albumin, and decyl-Sepharose with ovalbumin and phycoerythrin; the amount of protein bound to the adsorbent was taken as a measure of the hydrophobic interaction. The effects of the different ions on the adsorption of protein could, with one exception, be arranged according to the Hofmeister series. As the adsorption might also be influenced by alterations in the protein conformation, caused by the neutral salts, the proteins were studied by circular dichroism. Circular-dichroism spectra showed that 3 M sodium bromide and 3 M sodium thiocyanate changed the conformation of human serum albumin and ovalbumin, whereas 3 M sodium chloride and 1 M sodium sulphate did not. The conformational changes observed with sodium bromide and thiocyanate were accompanied by decreasing protein-adsorbent interaction, except for ovalbumin in 3 M sodium thiocyanate.