Thermoreactive Displacers for Anion Exchange and Hydroxyapatite Displacement Chromatography

A set of copolymers was prepared via radical copolymerization of N,N-dimethylacrylamide and 7-hydroxy-3-methyl-4-vinylindanone. While poly (N,N-dimethylacrylamide) is water-soluble at all temperatures, the copolymers showed a lower critical solution temperature (LCST), which depended on the composition. Independent of this LCST all copolymers can be used in the dissolved state as protein displacers in combination with anion exchange stationary phases. The indanone group of the polymers is known the chelate calcium ions. It was therefore also possible to use the polymers to displace acidic (i.e., C-site interacting) proteins from hydroxyapatite. The major advantage of the described displacers over existing agents stems from the fact that they can be almost quantitatively recovered by thermoprecipitation from the carrier but also from any given protein zone. Lowering of the temperature renders the polymers again fully soluble and ready for use. No unspecific protein coprecipitation was observed under these conditions within our analytical means.