Stimuli-responsive separation of proteins using immobilized liposome chromatography

The possibility of the stimuli-responsive separation of proteins was investigated using immobilized liposome chromatography (ILC) as novel aqueous two-phase systems. The specific capacity factor (ks) of β-galactosidase, obtained by analysis of ILC, was varied by changing the pH of the solution and was maximized at the specific pH of 5 (ks,max=5.57). The ks values were found to correspond well with their local hydrophobicities, which can be determined by the aqueous two-phase partitioning method. The variation of ks, therefore, indicates a change in the surface properties of a protein during conformational change under pH stimuli. A similar phenomenon is observed in the case of other proteins (α-glucosidase, ks,max=11.3 at pH 4; carbonic anhydrase from bovine, ks,max=6.53 at pH 4). The difference in the height and/or the position of the peaks of the ks–pH curves of each protein suggests a difference in their pH denaturation in the ILC column. Based on these results, the mutual separation of the above proteins at pH 4 could be successfully performed by selecting their specific capacity factor as a design parameter.