Mass influences in the performance of oligomeric poly(diallyldimethylammonium chloride) as displacer for cation-exchange displacement chromatography of proteins.

A novel type of linear polyelectrolyte, namely poly-DADMAC [poly(diallyldimethylammonium chloride)], was prepared and studied as a displacer for cation-exchange displacement chromatography of proteins. In contrast to the commercially available polymers of that chemistry, the novel type of poly-DADMAC introduced here is characterized by a homogeneous linear structure, a narrow distribution of the (adjustable) molar mass as well as by a defined and homogeneous affinity for the stationary phase. Five poly-DADMACs of different size (17900 to 88000 g/mol) were prepared and compared with regard to their stationary phase affinity and protein separation potential, taking a mixture of basic proteins, namely lysozyme, cytochrome C, and ribonuclease A (from bovine pancreas), as an example. The steric mass action model was employed to aid method development. Under the chosen conditions (low ionic strength of the mobile phase guaranteeing strong binding of both the proteins and the displacer) the poly-DADMAC with the lowest molar masses proved to be the most efficient displacers for the basic proteins with a stationary phase affinity constant of 5.3 x 10(16) and a steric factor of 224. Using this substance as displacer, a sample mixture containing up to three proteins was separated and the proteins recovered at high yields (80-97%) and in high purity and concentration.